topic 6 flash cards

what are the branches of the nervous system

CNS - brain and spinal cord

PNS - somatic

PNS - autonomic - sympathetic - parasympathetic

define reflex

where the body responds to a stimulus without making a conscious decision

define stimulus

something that can detected by an organism

define receptor

an organ or specialised cell that can detect the change causing the stimulus

define taxis

a response that involves movement in a specific direction

what is a positive and negative taxis

positive - where the organism moves towards the stimulus

negative - where an organism moves away from a stimulus

what is an example of taxis

gravitaxis - gravity 

define kinesis

a response that involves movement but in random direction, the speed and frequency of direction change increase

what is an example of kinesis

a woodlouse in a dry area speeds up and changes direction more frequently to find a damper area

define tropism 

a growth response controlled by a direction stimulus

explain photo tropism in the shoots

IAA moves to the shaded side of the shoot causing the shoot to elongate and bend towards the light as the plants shoots are POSITIVLY PHOTOTROPIC

explain photo tropism in the roots 

IAA moves to the shaded side growth is inhibited and the root beds away from the light as roots are NEGATIVLY PHOTOTROPIC

explain gravitropism in the shoot

IAA moves to the low side of the shoots causing the cell to elongate and grow upwards as they are NEGATIVLY GRAVITROPIC

explain gravitropism in the roots

IAA increases in the lower side causing growth to be inhibited and the root to grows downwards

what are Pacinian corpuscles

mechanoreceptors which detect pressure in the skin 

what is the first step in the Pacinian corpuscle creating a generator potential

there are stretch-mediated sodium ion channels in the membrane

what is the second step in the Pacinian corpuscle creating a generator potential

lamellae deforms

what is the third step in the Pacinian corpuscle creating a generator potential

sodium ion channels open

what is the fourth step in the Pacinian corpuscle creating a generator potential

sodium ions diffuse in

what is the fifth step in the Pacinian corpuscle creating a generator potential

sodium ions cause depolarisation which creates a generator potential 

what does myogenic mean

the ability to initiate its own contraction

describe the process of control of regular heart beat

the SA node initiates a rhythm by releasing a electrical impulse through the atrial walls causing both atria to contract at the same time 

the AV node relays the electrical impulse after a short delay to make sure all the blood has left the atria 

the impulse is then conducted down the bundle of HIS to the Purkinjee fibres in the ventricle walls

this causes the ventricles to contract from the bottom up 

how should you answer a question on receptors to increase heart rate

give same answer as pe - give an example - chemo or baroreceptors

explain how the sodium potassium pump maintains resting potential 

the sodium potassium pump using ATP to transport 3 sodium ions out of the cell and 2 potassium ions into the cell 

this leads to the inside of the cell being more negatively charged

the outside is more positively charged as some potassium ions are released through the potassium ion channels

what is the first step in forming an action potential

depolarisation - a stimulus causes sodium ion channels to open causing sodium ions to move into the cell down the concentration gradient making the inside of the neurone more positive

what is the second step in forming an action potential

if the potential reaches the threshold more sodium ion channels open and more sodium ions diffuses into the neurone

what is the third step in forming an action potential

repolarisation - sodium ion channels close and potassium ion channels open causing potassium ions to diffuse out of the neurone

what is the fourth step in forming an action potential

hyperpolarisation - potassium ion channels are slow to close causing too many potassium ions to diffuse out leading to the neurone becoming more negative than resting potential

what is the fifth step in forming an action potential

resting potential - sodium potassium pump returns the neurone to resting potential 

what is a refractory period and when does it occur

ion channels are recovering and cant be opened

occurs between hyperpolarisation and resting potential

describe the all or nothing law

An action potential is only generated when threshold is reached and will fire with same voltage no matter the size of the stimulus

describe how myelination occurs

saltatory conduction can occur where the neurones cytoplasm conducts enough electrical charge to depolarise the next next so the impulse jumps from node to node

how does an impulse travel along a non myelinated axon

depolarisation occurs along the whole axon making it slower than saltatory conduction

how does axon diameter effect the speed of an action potential

the bigger the diameter the less resistance so depolarisation occurs quicker in each part of the neurone

how does temperature affect the speed of an action potential 

if temperature is increased the ions diffuse more rapidly until around 40 degrees where proteins begin to denature and decreases speed 

what is the 1st step in synaptic transmission of ach across of cholinergic synapse and what does it cause

an action potential arrives at the synaptic knob and depolarises the pre synaptic membrane.

this causes voltage gated calcium ion channels to open causing calcium ions to diffuse into the synaptic knob

what is the 2nd step in synaptic transmission of ach across of cholinergic synapse and what does it cause

the influx of calcium ions cause the vesicles to fuse with the presynaptic membrane

this causes the vesicles to release acetylcholine into the synaptic cleft 

what is the 3rd step in synaptic transmission of ach across of cholinergic synapse and what does it cause

acetylcholine diffuses across the synapse and bind to the complimentary receptors on the post synaptic membrane

this causes sodium ion channels to open on the post synaptic membrane causing an influx of sodium ions

what is the 4th step in synaptic transmission of ach across of cholinergic synapse and what does it cause

the influx of sodium ions causes depolarisation of the post synaptic membrane 

this causes an action potential to be generated in the post synaptic membrane if the threshold is met

what is the 5th step in synaptic transmission of ach across of cholinergic synapse

the enzyme acetylcholinesterase hydrolyses the remaining acetylcholine into products which are reabsorbed into the pre synaptic membrane

what effect occurs when drugs are the same shape as a neurotransmitter

they mimic neurotransmitter causing more receptors to be activated

what effect occurs when drugs block the receptors

receptors cant be activated or only a few so muscle cells cant be stimulated causing paralysis

what effect occurs a drug inhibits an enzyme that breaks down a neurotransmitter 

the causes more neurotransmitter to bind to the receptors 

what is the function of tendons

non elastic tissue that connects muscle to bone

what is the function of ligaments

elastic tissue that connects bone to bone

what happens in an antagonistic muscle pair

one muscle relaxes while the other contracts

what is the structure of muscles myofibrils

are A band light or dark 

dArk 

are I band light or dark

lIght

what are the 3 difference between a neuromuscular junction and cholinergic synapse

Post synaptic membrane has clefts which store acetylcholinesterase

Post synaptic membrane has more receptors.

acetylcholine is always excitatory so a motor neurone action potential will result in a response in the muscle

what is the 1st step of muscle contraction

an action potential depolarises the sarcolemma and down the T-tubules

this cause a release of calcium ions

what is the 2nd step of muscle contraction

calcium ions cause tropomyosin to change shape

this exposes the myosin binding site

what is the 3rd step of muscle contraction

the myosin head binds to the actin filament forming a cross bridge