HUMAN PHYSIOLOGY EXAM QUESTIONS

Question 1

EXPLAIN THE RELATIONSHIP BETWEEN STRUCTURE AND FUNCTION OF ARTERIES

Answer 1

thick walls to withstand high pressure

collagen fibres give wall

strength/flexibility to stretch and recoil

muscle layer to maintain P

narrow lumen maintains high pressure

Question 2

EXPLAIN THE RELATIONSHIP BETWEEN STRUCTURE AND FUNCTION OF CAPILLARIES

Answer 2

wall has one layer of cell allowing fast diffusion of substances

pores to increase permeability

extensive branching increase S.A for exchange of materials

smaller diameter allows them to fit between cells

Question 3

EXPLAIN THE RELATIONSHIP BETWEEN STRUCTURE AND FUNCTION OF VEINS

Answer 3

thin walls allow muscles to exert pressure on veins

thin outer layer of collagen/ muscle/ elastic fibres provide structural support

wide lumen allows for great volume of blood to pass

valves prevent backflow

Question 4

OUTLINE HOW LEUCOCYTES DEFEND THE BODY AGAINST PATHOGENS

Answer 4

leucocytes/ phagocytes can recognize pathogens

phagocytes engulf pathogens by endocytosis/phagocytosis

each pathogen has specific antigens

leucocytes/ lymphocytes produce antibodies be reacting to specific antigen

antibody joins to antigen destroying them

lymphocyte makes clone/copies of itself

thus increasing numbers of antibodies

Question 5

EXPLAIN THE MECHANISM OF VENTILATION IN THE LUNGS IN ORDER TO PROMOTE GAS EXCHANGE FOR CELL RESPIRATION

Answer 5

inhalation brings air into lungs

external intercostal muscles contract

and move rib cage upwards and outwards

diaphragm flattens/ contracts

increasing thoracic volume

pressure decreases from atmospheric pressure so air rushes into lungs

exhalation forces air out

internal intercostal muscles relax/ external intercostal muscles and diaphragm relax

abdominal muscles contract and push diaphragm up

decreasing thoracic volume

increase lung pressure so air is forced out

a concentration gradient between air sacs and blood needs to be maintained

Question 6

EXPLAIN THE CONTROL OF BODY TEMPERATURE IN HUMANS

Answer 6

normal body core temperature constant (37)

regulate by negative feedback

hypothalamus is the centre of thermoregulation

hypothalamus sends impulses to the body to increase/ decrease temperatures

release of sweat if the skin temp rises

evaporation of water cools the body

heat is transferred by blood

vasodilation if temp rises

vasoconstriction if temp decreases

shivering increases heat production

Question 7

STATE THE SOURCE, SUBSTRATE AND OPTIMAL PH CONDITION FOR LIPASE IN THE HUMAN DIGESTIVE SYSTEM

Answer 7

source: pancrease
substrate: triglycerides/ lipids/fats/oil
product: glycerol and three fatty acid
optimal ph: 8

Question 8

DESCRIBE THE DIGESTION OF FOOD IN THE HUMAN DIGESTIVE SYSTEM

Answer 8

chewing food makes smaller particles

starch digestion begins in the mouth by salivary amylase

digestion of proteins in the stomach

acid condition in stomach provides optimum pH for enzymes

stomach muscle contraction causes mechanical digestion

enzymes in small intestine complete digestion

alkaline conditions in S.I provide optimum pH for enzymes

bile salts help to emulsify fats

example: amylase/protease/lipase with source substrate and products

Question 9

OUTLINE THE CONTROL OF THE HEARTBEAT BY THE NERVOUS AND ENDOCRINE SYSTEM

Answer 9

myogenic muscle contraction

contracts without stimulation

pacemaker/SAN in wall of right atrium

initiates contraction

nerves from brain transmit messages to pacemaker

to alter the rate of the pacemaker

medulla of the brain controls the heart rate

adrenaline is hormone produced by adrenal gland

adrenaline accelerates the heart rate

Question 10

EXPLAIN THE PRINCIPLES OF SYNAPTIC TRANSMISSION

Answer 10

Ca ions enter presynaptic neuron

release of neurotransmitter

from pre-synaptic neuron

diffusion across cleft/gap

to post synaptic neuron

binding to the neurotransmitter to receptors

change in membrane permeability

Na ions flow into post synaptic neuron

depolarization of post synaptic membrane

initiation of action potential

removal of the neurotransmitter

by enzyme

inactivated neurotransmitter returns to pre synaptic neuron

Question 11

OUTLINE THE ROLE OF HORMONES IN THE MENSTRUAL CYCLE

Answer 11

FSH stimulates follicle growth

egg cells mature

cell of growing follicle produce estrogen

estrogen signals lining of uterus to thicken

causes final maturation of follicle

high levels of estrogen stimulate secretion of LH

LH spikes stimulates ovulation

LH stimulates follicle to dev into corpus luteum

LH stimulates corpus luteum to secrete progesterone and estrogen

progesterone/estrogen stimulate continued dev/maintenance of lining of uterus

if no pregnancy occurs then corpus luteum dis-integrates

drop in progesterone/ estrogen hormone levels cause breakdown in uterine lining= menstruation

progesterone/ estrogen inhibit FSH/LH release

Question 12

DIABETES TYPE I AND TYPE II

Answer 12

type I caused by destruction of insulin secreting cells (beta)/ genetic disorder
early onset
treat with insulin

type II caused by decrease response of body cells to insulin
adult onset
treat with diet/lifestyle

Question 13

DISCUSS THE ETHICAL ISSUES ASSOCIATED WITH IVF

Answer 13

:)
infertile couples can conceive
allows children who are genetically related to them
decision to have children is clearly a conscious one
screening of embryos decreases chances of disease
increases reproductive age
cancer patients can harvest ova/sperm before chemo
production of extra embryos may be used for research

:(
potential risk from drug treatment
IVF unnatural procedure/ against some religions
infertility may be heritable and passed on to offspring
spare embryos are destroyed = murder?
production of extra embryos raises economic/legal ?
higher risk of multiple births/birth defects
expensive = exclusive

Question 14

EXPLAIN THE PROCESS OF TRANSLATION LEADING TO POLYPEPTIDE FORMATION

Answer 14

genetic code consists of codon of base triplets

mRNA is complementary to DNA strand

mRNA carries information (transcribed) from the DNA gene

translation occurs in a ribosome

mRNA attaches to the small subunit of the ribosome

has specific codons

each codon codes for one amino acid

tRNA matches its anticodons with the codons of the mRNA

by hydrogen bonds between complementary bases

each tRNA carries specific amino acid

the amino acids area attached to each other by condensation reactions/ peptide bonds

process is repeated

forming polypeptides

Question 15

OUTLINE HOW NERVE IMPULSES ARE TRANSMITTED ALONG A NERVE FIBRE

Answer 15

Na channels open and Na+ diffuses into the neuron down a concentration gradient

inside of the neurone become positive compared to the outside of the neuron: potential is reversed/ depolarization

wave of depolarisation moves down the membrane

K channels open and K+ diffuses out down concentration gradient

inside of neuron becomes negative compared with the outside/ potential across membrane restored/ repolarisation

active transport of K+ into neuron and Na+ out of neuron restores resting potential

Question 16

FUNCTION OF MOTOR NEURONS

Answer 16

carry electrical impulses from CNS to muscle glands

Question 17

RESTING POTENTIAL

Answer 17

neuron is not conducting an impulse

Question 18

DESCRIBE THE ACTION OF THE HEART PUMPING BLOOD

Answer 18

both atria collect blood from veins

SA node sends impulses to muscle initiating contraction

blood is pushed to ventricles by contraction of atria/ atrial systole

AV valves are open as atria contract

semilunar valves are closed so that ventricles fill with blood

ventricles contract/ ventricular systole

AV valves close (prevent backflow)

blood is pushed out through the semilunar valves/ into pulmonary artery and aorta

when ventricles relax/diastole, semilunar valves close preventing back flow of blood

simultaneous contraction

Question 19

NERVES CONNECTING THE BRAIN AND HEART CONTAIN NEURONS THAT CONTROL HEART RATE. EXPLAIN HOW A NERVE MESSAGE PASSES FROM ONE NEURON TO ANOTHER NEURON.

Answer 19

nerve impulses reaches the end of the presynaptic

depo causes Ca channels in membrane to open

Ca diffuses into the presynaptic neuron

vesicle of neurostransmitter move to and fuse with presynpatic membrane

neurotransmitter released by exocytosis into synaptic cleft/ space

neuroT diffuses across the space/ synapse

neuroT attaches to receptors on post synaptic neuron

receptors cause ion channels to open and Na diffuse into the postsynaptic neuron

post synaptic neuron is depolarized

depo causes a new action potential

neuroT on post synaptic membrane is broken down

neuroT is reabsorbed into the presynaptic neuron.

Question 20

(a) Outline the exchange of materials between capillaries and tissues.

Answer 20

a. molecules move by diffusion / move down a concentration gradient
b. nutrients move into tissues

c. gas exchange / Oxygen and carbon dioxide exchange between tissues and
blood/capillaries

d. (nitrogenous) wastes/excess water move from cells/tissues into blood/capillaries
e. hormones leave capillaries in target tissues/to attach to receptors on cells / (endocrine) organs/gland tissues release hormones into the bloodstream

Question 21

(b) Explain the structures and functions of arteries and veins.

Answer 21

a. arteries and veins have three layers in their walls
OR
walls of arteries and veins have tunica externa, media and intima
b. pressure is high in arteries/pressure is low in veins
c. arteries receive blood from ventricles/heart / carry blood away from heart
d. lumen of artery is small to keep pressure high
e. arteries have thick (muscular) walls (with elastic fibres) to withstand pressure
f. elastic fibres recoil in response to ventricle/heart contraction
g. muscle / elastic fibres help maintain pressure between heartbeats
OR
muscle / elastic fibres help propel blood toward capillary beds
h. veins receive blood from capillaries/capillary beds / carry blood to heart
i. large lumen of veins so there is less resistance to blood flow
j. valves in veins keep blood flowing toward heart/prevent backflow

Question 22

(c) Describe what happens in alveoli

Answer 22

gas exchange

b. oxygen diffuses from air to blood and carbon dioxide diffuses from blood to air
c. oxygen binds to hemoglobin in red blood cells
d. pressure inside/volume of alveoli increases/decreases / air enters/exits alveoli during inspiration/ expiration/ventilation

e. blood flow through capillaries / concentration gradients of
gases/oxygen/CO2 maintained

f. type II pneumocytes secrete fluid/surfactant / secretion of surfactant to
prevent sides of alveolus adhering