Nervous System

Question 1

Functions of Myelin Sheath

Answer 1

insulation, protection and impulse speed increaser

Question 2

Neurilemma

Answer 2

layer that helps in the repair of injured nerve fibres, wrapped around the Schwann cells

Question 3

Neuromuscular Junction

Answer 3

‘synapse’ between an axon and a skeletal muscle cell.

Question 4

Functional Neuron types

Answer 4

Sensory - carry nerve impulses from receptors in sense organs or skin into CNS
Motor - carry nerve impulses from CNS to effectors (muscles and glands)
Interneuron - carry nerve impulses between sensory and motor neurons

Question 5

Structural Neuron types

Answer 5

Multipolar - 1 axon, multiple dendrites, includes most interneurons and motor neurons
Bipolar - 1 axon, 1 dendrite (both may have branches at ends), occur in eye, ear and nose taking impulses from receptors to other neurons
Unipolar - 1 axon (not found in humans)
Pseudounipolar - 1 axon that splits into two extensions (one end with dendrites and the other with dendrites), includes most sensory neurons

Question 6

Neuron

Answer 6

nerve cell

Question 7

Nerve fibre

Answer 7

any long extension of cytoplasm of a nerve cell body - though it usually refers to the axon

Question 8

Nerve

Answer 8

bundle of nerve fibres held together by connective tissue. called tracts within the CNS, nerves outside it

Question 9

Extracellular fluid contains?

Answer 9

high concentration of sodium ions (10x higher outside than in). sodium diffusion = limited due to low number of sodium leakage channels

Question 10

Intracellular fluid contains?

Answer 10

low concentration of sodium ions, but contains potassium ions (30x higher inside than out). potassium diffusion = easy due to high number of potassium leakage channels

Question 11

Resting Membrane Potential value

Answer 11

around -70mV (i.e. potential inside is 70mv less than outside; it is polarised)

Question 12

RMP cause

Answer 12

differences in the distribution of sodium and potassium ions (extracellular fluid = more positive than intracellular)

Question 13

Sodium-potassium pump

Answer 13

carrier protein which moves 2 potassium ions in for every 3 sodium ions removed, i.e. causing a net reduction of positive ions into the cell. against concentration gradient, therefore is active transport and requires ATP

Question 14

Action potential definition

Answer 14

rapid depolarisation and repolarisation of the membrane caused by opening and closing of voltage-gated channels

Question 15

Depolarisation (AP)

Answer 15

sudden increase in membrane potential if level of stimulation exceeds 15mV. some sodium channels are opened (ligand- or mechanical-gated) and sodium ions move into cell. if stimulus is strong enough to increase MP to -55mV, voltage-gated sodium channels open, allowing for independent movement of sodium ions into the cell (all or none response). MP reaches +40mV.

Question 16

Repolarisation (AP)

Answer 16

soon after depolarisation, sodium channels close and voltage-gated potassium channels open, increasing flow of them out of cell. MP decreases again back to -70mV.

Question 17

Hyperpolarisation (AP)

Answer 17

after repolarisation, potassium channels remain open for longer than is needed; MP decreases further than RMP.

Question 18

Refractory Period

Answer 18

once sodium channels are opened, they are quickly inactivated (i.e. unresponsive to stimulus)

Question 19

Transmission of Nerve Impulse

Answer 19

depolarisation of one area causes movement of sodium ions into adjacent areas. this stimulates the opening of voltage gated sodium channels in next part of membrane, initiating a new action potential in said part.

Question 20

Saltatory Conduction

Answer 20

Because ions cannot diffuse in myelinated areas, they simply jump from one node of Ranvier to the next. this allows myelinated fibres to carry nerve impulses faster than unmyelinated ones

Question 21

Transmission across Synapse

Answer 21

1. nerve impulse activates voltage gated calcium ion channels
2. calcium ions flow into the cell at the pre-synaptic axon terminal
3. synaptic vesicles resultantly fuse with the membrane, releasing neurotransmitters by exocytosis
4. neurotransmitters diffuse across synaptic cleft and attach to receptors.
5. this stimulates ligand-gated protein channels to open which allow for the influx of sodium ions, initiating a new action potential in the post-synaptic membrane.

Question 22

Thermoreceptors

Answer 22

responsive to heat and cold, occurring mainly in the skin.

Question 23

Osmoreceptors

Answer 23

responsive to the concentration of substances dissolved in the water of the blood plasma. located in the hypothalamus.

Question 24

Chemoreceptors

Answer 24

responsive to particular chemicals. present in the nose - odours, present in the mouth - tastes, present internally - composition of bodily fluids, present in blood vessels - pH of blood and gas concentrations

Question 25

Touch receptors

Answer 25

responsive to changes in pressure and vibrations, or simply movements of hairs. found mainly in the skin.

Question 26

Pain receptors

Answer 26

responsive to damage to tissues, poor blood flow to tissues, or excessive stimulation of things like chemicals or heat. heavily concentrated in the skin and mucous membranes, most organs except for the brain.

Question 27

Reflex properties

Answer 27

rapid, stereotyped, triggered by stimuli and involuntary

Question 28

Protection of the CNS

Answer 28

cranium, the meninges and cerebrospinal fluid

Question 29

Meninges

Answer 29

layers of connective tissues covering the surface of brain and spinal cord

Question 30

dura mater of meninges

Answer 30

outer layer, tough and fibrous (sticks close to cranium but not so much in vertebral canal)

Question 31

arachnoid mater of meninges

Answer 31

middle layer, loose mesh of fibres

Question 32

pia mater of meninges

Answer 32

inner layer, more delicate and contains many blood vessels

Question 33

cerebrospinal fluid

Answer 33

clear, watery fluid containing a few cells aswell as urea, glucose, protein and salts. it acts as a shock absorber, it suspends the brain and provides nutrients/ gets rid of wastes

Question 34

Cerebrum

Answer 34

cerebral cortex: thinking, reasoning, learning, memory, intelligence and sense of responsibility, perception of senses and initiation and control of voluntary muscle contraction sensory areas interpret impulses from receptors, motor areas control muscular movements and association areas are concerned with intellectual and emotional processes

Question 35

basal ganglia

Answer 35

grey matter deep inside the cerebrum, play a role in initiating desired movements and inhibiting unwanted ones.

Question 36

frontal lobe

Answer 36

thinking, problem solving, emotion, personality, language, control of movement

Question 37

parietal lobe

Answer 37

processing temperature, touch, taste pain and movement

Question 38

temporal lobe

Answer 38

processing memories and linking them with senses, receives auditory information

Question 39

occipital lobe

Answer 39

vision

Question 40

insula

Answer 40

recognition of different senses and emotions, addiction and psychiatric disorders

Question 41

corpus callosum

Answer 41

joins left and right hemispheres of the brain allowing for communication between them

Question 42

cerebellum

Answer 42

under rear part of cerebrum, controls posture, balance, fine coordination of voluntary muscle movement.

Question 43

hypothalamus

Answer 43

control homeostasis and many bodily activities, including blood pressure and heart rate, body temperature, contraction of bladder, sleeping, food and water intake, endocrine system, emotion

Question 44

medulla oblongata

Answer 44

continuation of the spinal cord, contains the cardiac centre, respiratory centre and vasomotor centre, which respectively control the rate and force of heartbeat, the rate and depth of breathing and the diameter of blood vessels

Question 45

ascending tracts (spinal cord)

Answer 45

sensory axons carrying impulses upwards towards the brain

Question 46

descending tracts (spinal cord)

Answer 46

motor axons carrying impulses downwards away from the brain

Question 47

division of peripheral nervous system

Answer 47

afferent and efferent

Question 48

afferent division

Answer 48

involves sensory neurons carrying impulses into the CNS somatic sensory neurons carry impulses from the skin and muscles. visceral sensory neurons carry impulses from the internal organs

Question 49

efferent division

Answer 49

involves motor neurons carrying impulses away from the CNS autonomic division involves carriage of impulses to heart muscle, involuntary muscles and glands. (2 neurons) somatic division involves carriage of impulses to skeletal muscles (1 neuron)

Question 50

autonomic division (efferent)

Answer 50

sympathetic - fight or flight, activated when in times of strenuous activity, prepares body for such times. neurotransmitter involved = acetylcholine parasympathetic - rest and digest, activated when in times of quiet activity; more regular bodily activities, controlling its constant, internal environment. neurotransmitter involved = noradrenaline