Further Human physiology

Question 1

Example of a hormonal steroid

Answer 1

Oestrogen - Increase thickness of uterine lining

Hormonal steroids: Enter cells and result in a modification in cell protein synthesis within the cells.

Question 2

Example of a hormonal peptide (protein)

Answer 2

Insulin - Promote glucose uptake by body cells

Hormonal proteins: They do not enter cells. They bind to a receptor protein on the cell membrane surface.

Question 3

Example of hormonal tyrosine derivative

Answer 3

Thyroxin - Increases metabolic rate

Question 4

How do hormonal steroids function?

Answer 4

They enter cells and result in a modification in cell protein synthesis within the cells.

Question 5

How do hormonal peptide (proteins) function?

Answer 5

Peptide hormones (protein hormones) do not enter cells. They bind to a receptor protein on the cell membrane surface.

Question 6

Mode of action peptide hormone

Answer 6

a) Attachment to plasma membrane receptor ( Glycoprotein)
(b) Receptor-Hormone complex: A receptor protein binding with a hormone forms a hormone- receptor complex.
(c) Stimulation of secondary messenger in cytoplasm which alters the action of the cell.

Question 7

Mode of action steroid hormone

Answer 7

(a) Pass straight through the plasma membrane

Directly affect the expression of genes (protein —–synthesis)

Question 8

Relationship between hypothalamus and pituitary gland

Answer 8

The hypothalamus controls the hormonal secretion to the pituitary.
The hypothalamus has many receptors for changes of internal conditions and serves as a link between the nervous system and the endocrine system (pituitary).

Question 9

What is secreted by the gastric glands into the alimentary canal?

Answer 9

Gastric glands: Secrete mucus, hydrochloric acid and pepsinogen from the inner lining of the stomach. Starts protein digestion.

Question 10

What is secreted by the liver (liver is a gland) into the alimentary canal?

Answer 10

The liver: Secretes bile into small intestine. Bile comes from liver or gall bladder. It emulsifies lipids and increases surface area of lipids for the action of lipase.

Question 11

Explain the structural features of exocrine gland cells

Answer 11

Exocrine gland cells: Secrete product into a duct to be transported to a specific location.

The exocrine gland cells (secretory cells) surround the end of a ‘‘small branch’’ which is a ductile. The secretory cells secrete digestive enzymes into the ductile by vesicles. This ductile then leads to a larger duct which leads to the pancreatic duct ‘‘stem of the tree’’. Exocrin gland cells have a lot of mitochondria because exocytosis require ATP. THey go thorough the entire process, transcription, translation at R.E.R, synthesis in golgi apparatus (cis to trans side, through cisternae) and then vesicle formation for exocytosis.

One ‘‘branch’’ is called acinus.

Question 12

State the composition of Saliva

Answer 12

The solvent is water

Enzyme is amylase

Contains mucus

Question 13

State the composition of Gastric Juice

Answer 13

The solvent is water

Enzyme is pepsin (inactive form is pepsinogen)

Contains hydrochloric acid which removes Pepsin from Pepsinogen and makes it active

Contains mucus

Question 14

The control of digestive juice secretion by nerves and hormones

Answer 14

Pre - ingestion
The sight and smell of food triggers a reflex reponse in which gastric juice is secreted from gastric pits in the stomach wall. This ensures that gastric juice is in the stomach by the time food is consumed.

Post - ingestion
Food entering the stomach causes distension, which is detected by stretch receptors (nerves) in the stomach lining. Impulses are then sent to the brain, which triggers the secretion of gastrin from its lining the stomach wall. Gastrin in its turn causes the sustained release of gastric juice, particularly its acid component. When the pH drops too low, gastrin secretion is inhibited by hormones. Gastric juice lowers the pH (hydrochloric acid).

Question 15

Why can we humans not digest cellulose in the alimentary canal?

Answer 15

Cellulose is a polysaccharide carbohydrate which is digested by cellulase which is produced by mutualistic microorganisms. We do not have a relationship with the type of bacteria that produces cellulase thus we cannot digest cellulose.

Question 16

How is Pepsin activated from its inactive precursor Pepsinogen?

Answer 16

Pepsin is primarily synthesized as a primary structure with 44 other amino acids (pepsinogen). When it is exposed to hydrochloric acid the other amino acid are removed and only pepsin remains and thus becomes activated.

Question 17

The role of bile in lipid hydrolysis and digestion

Answer 17

Lipase can only catalyse the hydrolysis of the lipids on the outer part of the lipid globule, which means that the interior is mostly inaccessible to the enzyme. Bile produced by the liver have both hydrophobic and hydrophilic end. They insert themselves between lipid molecules and prevent them from coalescing into larger globules. Thus bile is an emulsifier that beaks up relatively large accumulations of lipids into smaller droplets.

This increases the lipid surface area!

Lipase is also both polar and non-polar. ‘

Question 18

List the materials that are not absorbed and are egested

Answer 18

Some substances cannot be digested thus never absorbed. They become a part of the solid waste or faeces.

They include: 
Cellulose
Lignin (component of plant wall cells)
Bile pigments
Bacteria 
Intestinal cells

Question 19

Main function of the Hepatic Artery

Answer 19

Hepatic artery: branch from the aorta (oxygenated blood) to the liver capillaries (sinusoids).

Question 20

Main function of the Hepatic Portal Vein

Answer 20

Hepatic portal vein: carrier deoxygenated blood absorbed with nutrients from intestines to liver capillaries (sinusoids). Low pressure.

Question 21

What are sinusoids?

Answer 21

Sinusoids: Capillaries in liver

Question 22

Main function of the Hepatic Vein

Answer 22

Hepatic vein: Drains sinusoids deoxygenated blood to venae cava and right atrium of heart. This blood does not have much nutrients.

Question 23

How can hepatocytes regulate levels of nutrients in blood

Answer 23

The body produces certain hormones which causes the hepatocytes to add or remove these substances from the blood to keep the solute concentration within the normal range.

E.g. insulin causes hepatocytes to convert glucose to glycogen lowering glucose concentrations in blood and glucagon from the pancreas causes the glycogen to be converted back to glucose to increase the concentration.

Question 24

Function of sinoatrial node

Answer 24

This node contains modified cardiac muscle cells which send out action potentials across both atriums causing them to undergo systole. The action potential also reaches the atrioventricular node.

Approximately 0.1 seconds after receiving the first action potential this node sends out its own action potential through the septum between the ventricles eventually branching out to conducting fibres going around the thick cardiac muscle tissue of both ventricles causing them to undergo a much more powerful systole.

Question 25

Position of atrioventricular node

Answer 25

atrioventricular node which is positioned close to the middle of the heart in the bottom of the right atrium.

Question 26

Position of the sinoatrial node

Answer 26

Sinoatrial node is positioned in the right atrium where the blood from the venae cava enters.

Structure/function: This node contains modified cardiac muscle cells which send out action potentials across both atriums causing them to undergo systole

Question 27

What is myoglobin?

Answer 27

Oxygen-binding protein found in muscles

Consists of 1 polypeptide, one haem groups, and one iron atom.

Function is to store oxygen within muscle until it enters a anaerobic situation and then dissociates oxygen to delay lactic acid fermentation

Question 28

Function of carbonic anhydrase

Answer 28

Carbonic anhydrase is an enzyme in the cytoplasm of erythrocytes: it catalyses the formation of carbonic acid (H2CO3) from carbon dioxide and water

Question 29

Chloride shift

Answer 29

Through facilitated diffusion by protein channels in erythrocytes cell membrane HCO3- exits the cytoplasm into the blood plasma through the cell membrane. To keep a balanced charge on either side of the membrane a chloride ion moves into the erythrocyte from the blood plasma. This exchange of two negative ions is known as the chloride shift.

Question 30

How does the body acclimatize itself at high altitudes and the issues arising at high altitudes?

Answer 30

Low partial pressure O2;
Haemoglobin do not become saturated;
Mountain sickness; Bodily tissues will not receive enough O2;

Increase production erythrocytes;
Haemoglobin has reduced affinity for O2/dissociates O2 more readily;
Increase in myoglobin production in muscle tissues to dissociates O2 during anaerobic conditions;
Incease surfade area of lungs for deeper breathing, more O2 uptake (exchange of gases in lungs)/ increase ventilation rate;
Increase ventilation rate;
Reduced activity to not overconsume ATP

Question 31

anterior pituitary

Answer 31

• neurosecretory cells secrete hormonones into capillaries in the Hypothalamus which are then carried by the portal vein to the anterior pituitary gland
• -> releasing hormones stimulate the anterior pituitary to secrete hormones e.g. GnRH stimulates the release of FSH and LH

Question 32

posterior pituitary

Answer 32

• neurosecretory cells synthesize hormones
• passed via axons to nerve endings in the pituitary gland
  e. g. secretion of ADH is controlled in this way

Question 33

Control of ADH secretion

Answer 33

1. neurosecretory cells in the hypothalamus synthesize ADH, transport it down their axons and store it in nerve endings in the posterior pituitary gland
2. osmoreceptors in the Hypothalamus monitor the concentration of the blood Plasma
3. ADH causes a reduction in the concentration of the blood plasma by stimulating the kidney to produce hypertonic urine
4. low blood concentration: release of ADH is not stimulated
   high blood concentration: release of ADH stimulated

Question 34

State hormones released from the Anterior vs Posterior pituitary gland

Answer 34

Anterior: FSH and LH
Posterior: Oxytocin and ADH (but produced in hypothalamus, sent down neurosecretory cells and stored at their axons until impulse is sent to release them).