VIII. Animal Physiology

Key focus of this chapter: digestion hormones

This chapter focuses on digestion hormones and gives concise summaries of the important things about respiration, cardiovascular system, osmoregulation and excretion, endocrinology, and nutrients.

A. Respiration

: process of gas exchange in the body.

  • Internal respiration

– cellular respiration.

– making ATP by using oxygen in mitochondria.

  • External respiration

– air passage into and out of lung.

– exchange of O2 and CO2 between lung and blood of the pulmonary capillaries.

– transportation of gases included in blood to body cells and lung by heart.

– exchange of O2 and CO2 between blood of the systemic capillaries and cells.

  • Figure of external respiration

1. Respiratory tract

a. Air Passage

b. Function of each part

Classification

Features and roles

Pharynx

• Muscular tube for passageway of digestion and respiration

Larynx

• Cartilage connective tissue for protection of the trachea

• Sound generating part

• Located between trachea and esophagus

Epiglottis

• Flap tissue to prevent food from entering the respiratory tract

Trachea

• Rigid structures composed of C-shaped ring of cartilage to keep air flow

• Wind pipe

Bronchi

• Lead air to each lung

Bronchioles

• Branches of bronchi

• Small and finer tubes

Alveoli

• Air sac for gas exchange between lung and capillary

2. Inspiration and expiration

a. Inspiration

  • The diaphragm moves downward and contracts
  • Lungs inflate with negative air pressure
  • Air moves into alveoli

b. Expiration

  • The diaphragm moves upward and expands
  • Lungs deflate with positive air pressure
  • Air moves out from alveoli

B. Cardiovascular System

1. Animal circulatory systems

Animal

Number of Chambers of heart

Number of Circuits

Fish

Two

One

Amphibians and Reptiles (Lizards, turtles, snakes)

Three

Two

Birds and mammals

Four

Two

2. Heart of mammal

a. The pathway of circulation

Watch blood flow through the human heart

b. Anatomy of heart

Classification

Features and roles

Atrioventricular valves

• Keep blood moving from atrium and to ventricle

• Prevent backflow into atrium

• Flap composed of connective tissue

Semilunar valves

• Keep blood moving from ventricle and to arteries (aorta, pulmonary artery)

• Prevent backflow into ventricle

• Flap composed of connective tissue

Intercalated disks

• Gap junction between two cells

• Provide action potential to whole heart muscle cells and contract whole heart

Atrium

• Chamber for receiving blood

Ventricle

• Chamber for pumping blood out

Conduction system

Sino-atrial node (SA node)

• Functions as pacemaker

• Located in the wall of the right atrium

• Initiates and controls the rate of heart beat to contract all heart muscles

Atrioventricular node (AV node)

• Located in the wall between right atrium and right ventricle

• Point for delaying signal to check that the atria is empty before contracting ventricles

c. Cardiac pressure

  • Systole – phage of ventricular contraction
  • Diastole – phage of ventricular relaxation
  • Cardiac output

– left ventricle pumps blood into the systemic capillaries (per minute)

– stroke volume × heart rate

  • Stroke volume

– amount of blood pumped from the ventricle

3. Blood vessels

a. Blood circulation in the blood vessels

 b. Functions of each part

Blood vessels

Features and functions

Artery

• Thick muscular wall and large vessel

• Transports blood from heart to arteriole

• Highest pressure

Arteriole

• Small vessel

• Transports blood from artery to capillary

• Branched from artery

• Determines the distribution of blood

Capillary

• Thin and smallest vessels with only endothelium tissues

• Highest area and lowest blood velocity

• Transports blood from arteriole to each body tissue

• Exchanges gases, nutrients, and wastes to body cells

Venule

• Thin and small vessel

• Collects blood from capillary

• The movements of skeletal muscles help return blood from capillary to heart in venule and vein

Vein

• Large vessel with low blood pressure

• Transports blood from venules to heart

• Has valves to prevent back flow

** Portal venous system

  • Transports blood from the capillaries to other capillaries via veins
  • Eg/ hepatic portal vein

c. Blood pressure

  • Main force for the circulatory blood movement 

d. Starling forces

  • Driving forces for the fluid movement into and out of capillaries
  • Capillary hydrostatic pressure and capillary oncotic pressure

Starling forces

Features and functions

Capillary hydrostatic pressure

• Driving force of fluid from capillary to interstitial fluid.

• The force is much greater than capillary oncotic pressure at arteriole end of capillary.

Capillary oncotic pressure

(Osmotic pressure)

• Driving force of fluid from interstitial fluid into capillary.

• Proteins of blood plasma in capillary pull water from interstitial fluid.

• The force is much greater than capillary hydrostatic pressure at the venule end of capillary.

4. Blood

a. Cellular elements (45 % of blood)

Cell types

Features and functions

Erythrocytes

(Red blood cells)

• Have hemoglobin to transport oxygen and carbon dioxide

• Lack nuclei and mitochondria

Leukocytes  (White blood cells)

-  cells of immune system

-  have nuclei

-  larger than red blood cells

-  can move into the lymphatic system from the blood vessels

Basophils

• Secrete chemicals (histamine and anticoagulant heparin) to allergic reactions or damaged tissues

Eosinophils

• Minor phagocytic activity

• Release enzymes to kill parasites

• Sometimes discharges toxins from enzyme damage to tissues

Lymphocytes

• Helper T cells – secrete cytokines to active B cells and cytotoxic T cells

• B cells – form plasma cells to secrete antibodies

• Cytotoxic T cells – secrete molecules (perforin) to kill infected or tumor cells

• Natural killer cells (Null cells)

 - release factors to kill infected or tumor cells

Monocytes

• Become macrophages for phagocytic activity

Neutrophils

• Phagocytosis of microorganism or foreign particles

Platelets

• Hemostasis - process of blood clotting

• Lack nuclei

 b. Plasma elements (55 % of blood)

Classification

Features and functions

Ion

• Regulation of osmotic balance, controlling of membrane permeability, pH buffering

• Eg/ Bicarbonate, chloride, sodium, potassium, calcium, magnesium

Plasma

proteins

Albumin

• Regulation of osmotic balance and pH buffering

Fibrinogen

• Formation of blood clotting

Immunoglobulins

• Antibodies for immune response

Water

• Solvent for transporting other materials

Other substances

• Nutrients, hormones, waste products

c. Transport oxygen

  • Hemoglobin

– consists of tetramer proteins in red blood cells.

– allosteric proteins.

– each subunit protein has a hemi group, which contains iron.

– hemi group binds O2 to transport.

– binding affinity of CO is greater than O2

 ** Myoglobin

– bind O2 to store in muscles.

– similar structure with hemoglobin but with monomer shape.

  • Oxygen – binding curve of hemoglobin

– increased O2 binding affinity means increased percent O2 saturation at the same rate of partial pressure of O2

– cooperativity with oxygen binding to hemoglobin.

– bohr shift means that O2 binding affinity of hemoglobin decreases with low pH (high CO2).

d. Transport carbon dioxide

  • Most CO2 (70%) from respiring cells is transported to lungs as bicarbonate ion (HCO3–) in the red blood cells
  • Small amount of CO2 (23%) is bound to hemoglobin and transported
  • The rest of CO2 (7%) is dissolved in plasma
  • The rate of pH in the blood is maintained by bicarbonate ion (HCO3–)
  • Exchanging O2 and CO2 by passive diffusion

e. States of red blood cells

f. Blood clotting

  • ① Clotting materials (Ca2+, vitamin K, platelets) convert a prothrombin to the active thrombin enzyme.
  • ② Thrombin enzyme converts an inactive fibrinogen to fibrin.
  • ③ Fibrin forms framework of clot at damaged tissue.

C. Digestion

1. Mouth

  • Mechanical breakdown of food by teeth.
  • Chemical breakdown by salivary amylase, which breaks down starch to disaccharides.
  • Moistening of food to form a bolus.

2. Esophagus

  • Conducts food from mouth to stomach by waves of muscular contraction called peristalsis.
  • Controls the passage of food by muscular ring valves called sphincter.

3. Stomach

  • Functions for storage and digestion.
  • Mechanical breakdown by churning movements.
  • Gastric glands secrete mucus from mucus cells, pepsinogen from chief cell, and hydrochloric acid (HCl) from parietal cells.
  • Pepsin, which is converted from pepsinogen by HCl, digests proteins.
  • Food mixed with gastric juice becomes acid chyme.
  • Mucus lubricates and protects the surface of stomach walls.
  • Cardiac orifice (Gastroesophageal sphincter) regulates back flow of food from stomach to esophagus.
  • Pyloric sphincter controls the passage of acid chyme from stomach to small intestine.

4. Small intestine

: most chemical digestion for all nutrients occurs in small intestine, which is composed of duodenum, jejunum, and ileum.

a. Secretion to duodenum

  • Pancreas – secretes pancreatic juice, which contains the digestive enzymes and bicarbonate for neutralizing the acid chyme, to duodenum.
  • Liver – secretes bile, which contains bile salt for digestion of fats, to duodenum.
  • Epithelium of small intestine – secretes digestive enzyme.

b. Absorption

  • Villi – highly folded mucosal projection to increase surface area for absorption.
  • Microvilli – microscopic projection on individual cells.
  • Fatty acid and glycerol are absorbed by lacteal and carried to blood via lymph vessel.
  • Glucose and amino acid are absorbed by blood capillary and carried to liver via hepatic portal vessel.

5. Liver

a. Secretion for digestion

  • Bile production and storage in gallbladder.
  • Bile contains bile salts and bicarbonate for helping lipid digestion as a function of the emulsifying agent but does not contain enzyme.

b. Multiple functions

  • Destruction of aged red blood cells.
  • Glycogen synthesis, breakdown, and storage.
  • Synthesis of plasma proteins such as albumin, clotting proteins, and angiotensinogen.
  • Conversion of ammonia or nitrogenous into urea (detoxification).
  • Elimination of waste or bacteria from blood.

6. Pancreas

a. Exocrine (excretion pancreatic juice to duodenum)

  • Secrete amylase to digest carbohydrate.
  • Secrete trypsin to digest protein.
  • Secrete lipase to digest fat.
  • Secrete bicarbonate ions to neutralize the acid chyme.

b. Endocrine (excretion hormones into blood stream)

  • α cells secrete glucagon to convert glycogen to glucose.
  • β cells secrete insulin to convert glucose to glycogen.

7. Large intestine (Colon)

  • Composed of four major parts, ascending colon, transverse colon, descending colon, and sigmoid.
  • Absorption of water, ions, and other minerals.
  • Feces transformation and storage of feces.
  • Absorption of vitamin K produced by harbor bacteria.

8. Overview of digestion

9. Hormonal control of digestion

Digestion hormones

D. Osmoregulation and excretion

  • Osmoregulation – regulates the concentration of water and solute.
  • Excretion – eliminates the nitrogen containing waste product from metabolism.

1. Animal osmoregulation and excretion

Classification of animal

Osmoregulation and excretion

Protonephridia

• Flame bulb

Earthworm

• Metanephridia

Insect

• Malpighian tubules

Bony fish

Freshwater fish

• Excreting a large amount of water by kidneys for water balance in the hypotonic environment

Saltwater fish

• Taking in a large amount of saltwater and depositing salt ions in the kidneys for water balance in the hypertonic environment

Bird

• Long loop of Henle to drink seawater

2. Mammal osmoregulation and excretion

a. Basic renal processes of mammal kidney

  • Filtration – filter the protein-free plasma from glomerulus to bowman’s capsule by active transport.
  • Secretion – transport toxins and excess salts from body fluids (peritubular capillaries) to renal tubules by active transport.
  • Reabsorption – transport filtrated substances from renal tubules to body fluids (peritubular capillaries) by active or passive transports.
  • Excretion – excrete filtrated substance from renal tubules to ureter.
Watch mammalian kidney

b. Function of each part

Classification of kidney process

Features and functions

Filtration
(active transport)

Glomerulus

• Ball shaped capillary tubes

• Glucose in protein-free plasma is filtered completely

Bowman’s capsule

• Cup shaped renal tubes

• Surround glomerulus

• Filter water glucose and small solutes (sodium and potassium ions, amino acids, urea)

• Cannot filter large molecules such as blood cells or plasma proteins

Secretion
(active transport)


and


Reabsorption
( active or passive

transport)

Proximal tubule

• Secretion and reabsorption of salt, nutrients (glucose and amino acid), and water

• Most of the reabsorption of water and salt occurs

• pH regulation


Distal tubule

• Secretion and reabsorption of salt and water

• Control K+ and NaCl

• pH regulation

• Aldosterone reabsorbs water and Na+ to increase blood pressure

Reabsorption
( active or passive

transport)

Descending loop of Henle

• Reabsorption of water

Ascending loop of Henle

• Reabsorption of NaCl

Excretion

Collection duct

• Collection of high concentration urea

c. Passage of waste products

E. Endocrinology

1. Hormone

: intercellular chemical signals produced by endocrine glands.

a. Hypothalamus hormones

  • Hormones between the nervous system of the hypothalamus and the blood capillaries of pituitary gland.

b. Steroid hormones

  • Hydrophobic with insoluble lipids in water.
  • Cross plasma membranes and bind to receptors in the nucleus.
  • Eg/ Androgens, Estrogens, Progesterone, cortisol, aldosterone

c. Peptide hormone

  • Hydrophilic and dissolved in water.
  • Cannot cross plasma membranes and bind to receptors on the surface of a target cell.
  • Eg/ Most hormones

d. Tropic hormones

  • Participate in the function of endocrine signaling.
  • Eg/ FSH, LH, TSH, ACTH, hypothalamus hormones

e. Nontropic hormones

  • Eg/ Endorphin, MSH, prolactin

2. Hormones of endocrine glands

Hypothalamus Hormones

Pituitary

Hormone

Target

Functions of pituitary hormones

GHRH (stimulates GH)

GHIH

(inhibits GH)

Anterior Pituitary

GH 

(growth hormone)

Liver and

bone

• Stimulates cell division and increasing cell size

TRH

(stimulates TSH)

TSH

(thyroid stimulating hormone)

Thyroid

• Controls homeostatic functions and cellular metabolism

 (digestion, heart rate, blood pressure, reproductive functions)

• Stimulates production of T3 and T4

CRH

(stimulates ACTH)

ACTH

Adrenal

cortex

• Responds to long term stress

• Stimulates secretion of corticosteroids (glucocorticoids, mineralocorticoids)

GnRH

(stimulates LH and FSH)

LH
(luteinizing hormone)

Testis and

ovary

• Causes the follicle to undergo ovulation

• Stimulates the Leydig cells for testosterone secretion in testes

FSH

(follicle stimulating hormone)

• Stimulates ovaries for primary follicle development

• Stimulates the sertoli cells for spermatogenesis in testes

PRH

(stimulation)
PIH

(inhibition)

Prolactin

Mammary

glands

• Stimulates mammary glands for milk production and secretion

MSH

Melanocytes

• Stimulates color changes of skin in reptiles and amphibians

Posterior

Pituitary

ADH

(antidiuretic hormone, vasopressin)

Kidney

tubules

• Stimulates the kidney for retention of water from renal tubules to body capillaries and increases blood pressure

• Causes concentrated urine

• Insufficient ADH causes Diabetes insipidus

Oxytocin

Mammary

glands,

uterine muscles

• Initiates milk release

• Induces labor

3. T3 and T4 from Thyroid Gland

: thyroid gland consists of two lobes sited on trachea and controls homeostatic functions and cellular metabolism such as digestion, heart rate, blood pressure, and reproductive functions.

  • Secretion of T3 and T4 from hypothalamus
  • Triiodothyronine (T3)

– has three iodine atoms.

– more powerful activation than T4.

  • Thyroxine (T4)

– has four iodine atoms.

– higher rate of production than T3.

– converted to T3 in kidney, liver, or target cells.

  • Metabolic disorders of the thyroid gland

Metabolic disorders

Causing and symptoms

Hyperthyroidism

• Excessive secretion of thyroid hormone

• High rate of metabolism with high temperature, poor emotional control, high blood pressure, irritability, profuse sweating, and weight loss

• Eg/ Graves’ disease (protruding eyes)

Hypothyroidism

• Insufficient secretion of thyroid hormone

• Low rate of metabolism with cold intolerance, lethargy, and weight gain

• Eg/ Myxedema, Cretinism in infants

4. Regulation of blood calcium levels

a. Parathyroid hormone (PTH)

  • Secreted by parathyroid gland when Ca2+ levels in blood are decreased.
  • Raises the blood calcium levels by osteoclasts of bone.
  • Raises the blood calcium levels from kidney and intestine stimulated by vitamin D.

b. Calcitonin

  • Secreted by thyroid gland when Ca2+ level in blood is increased.
  • Reduces the blood calcium levels by osteoblasts of bone and kidney.
  • Reduces the blood calcium levels from kidney.

5. Regulation of blood glucose levels

a. Glucagon

  • Secreted by alpha cells in pancreas when glucose levels in blood are decreased.
  • Conversion of glycogen to glucose.
  • Stimulates liver to release glucose into blood stream.

b. Insulin

  • Secreted by beta cells in pancreas when glucose levels in blood are increased.
  • Stimulates liver to absorb glucose from blood stream for low blood glucose.
  • Conversion of glucose to glycogen.

** Islet of Langerhans: composed of Alpha Cells, Beta cells, Delta cells, and F cells in pancreas

 6. Stress response

  • Regulated by adrenal glands in kidney

a. Adrenal medulla

  • Stimulated from hypothalamus via spinal cord.
  • Secretes epinephrine and norepinephrine to response short term stress.
  • Responds to high blood glucose, high blood pressure, rapid pulses, increasing metabolic rates.

b. Adrenal cortex

  • Stimulated by ACTH.
  • Secrete cortisol and aldosterone in response to long term stress.
  • Cortisol responds to high blood pressure and reabsorption of Na+ and water.
  • Aldosterone responds to with high blood glucose and decreasing immune system.
  • Aldosterone induces the reabsorption of water and sodium in the kidneys.

7. Other chemical messengers

a. Pheromones

  • Chemical substances communicated by odors outside the body.
  • Functions in marking territories, courtship behavior, classifying social order between same species.

 b. Renin

  • Proteolytic enzyme that regulates arterial blood pressure.
  • Often called as hormone.

c. Melatonin

  • Amino acid hormone secreted from pineal gland in brain.
  • Functions in circadian rhythms.
  • Secreted at night.

d. Endorphin

  • Neuropeptide of chemical signal.
  • Decreases pain perception in brain.

F. Nutrients

1. Vitamin

  • Organic compounds
  • Needed in small amounts, but problems with deficiencies
  • Not synthesized by animals

Vitamins

Types

Functions

Water-soluble

Vitamins

Vitamin B1

(thiamine)

• Participates in cellular respiration by removing CO2 from organic materials

• Contained in grains, peanuts, pork, and legumes

Vitamin B2

(riboflavin)

• Component of coenzymes FAD and FMN

• Metabolism for energy

• Contained in grains, vegetable, and meats

Vitamin B3

(niacin)

• Participates in element of NAD+ and NADP+ enzyme

• Contained in grains, nuts, and meats

• Insufficient amount results in pellagra disease

Vitamin C

(L-ascorbic acid)

• Involved in collagen synthesis

• Related with skin of body

• Insufficient amount results in scurvy disease

• Contained in fruits and vegetables

Fat-soluble

Vitamins

Vitamin A

(retinol)

• Component of visual pigment, retina of photoreceptor

• Insufficient amount results in vision problems

• Contained in green vegetables or orange

Vitamin D

• Involved in bone growth and immune system

• Made by skin from sunlight

• Contained in egg yolk

• Insufficient amount results in rickets disease

Vitamin E

(tocopherol)

• Involved in antioxidant, which is to protect cell membrane against oxidation reaction

• Insufficient amount results in anemia and sterility

• Contained in nuts, seeds, and vegetable oils

Vitamin K

(phylloquinone)

• Important component for blood clotting

• Mostly absorbed in the large intestine

• Contained in green vegetables

2. Minerals

  • Inorganic substances
  • Needed in small amounts, but cause problems in large amounts
  • Phosphorus, magnesium, calcium – important in bone and tooth formation
  • Sodium and potassium – function in muscle contraction and nerve conduction
  • Iron – binds oxygen in hemoglobin and components of electron carriers
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