B13 Flashcards
Transducer
Sensory receptor converts stimulus into a nerve impulse (generator potential).
Resting Potential
-70 mV. Polarised.
3 Na+ out/2K+ in (AT).
Inside of axon negative relative to the outside.
Action Potential
+40 mV. Depolarised.
Stimulus open Na+ channels, Na+ in, cause more to open.
At +40, close, open K+ channels, K+ diffuse out (hyperpolarisation). K+ close. Pump restores RP.
Propagation of AP
Stimulation causes depolarisation, which causes the depolarisation of the next region (Na+ attracted by -ve charge ahead).
Cont. and area behind returns to RP.
Saltatory Conduction
Myelinated faster as AP jumps to the nodes of Ranvier. Faster, more energy efficient (reduces amount of ATP needed for repolarisation).
All-or-nothing Principle
AP always same size.
Stronger stim = inc. freq. AP.
Stim needs to reach threshold value to trigger depolarisation.
Measure freq. with oscilloscope.
Excitatory Neurotransmitter
Depolarisation of postsynaptic.
Acetylcholine.
Inhibitory Neurotransmitter
Hyperpolarisation of postsynaptic.
Prevents AP being triggered.
GABA.
Spatial summation
Multiple presynaptic connect to 1 postsynaptic. Cause neurotransmitter levels to build, reaching threshold, trigger AP.
Temporal summation
Single presynaptic releases several times over a short period. Builds up in synapse until AP triggered.
Role of synapses
Ensure impulses unidirectional.
Transmit from 1 neurone to multiple.
Central Nervous System (CNS)
Brain and spinal cord. Relay neurones.
Peripheral Nervous System (PNS)
All the neurones that connect CNS to rest of body. Sensory and motor neurones.
Somatic Nervous System (part of PNS)
Conscious control. Input from sense organs, output to skeletal muscles.
Autonomic Nervous System (part of PNS)
Works constantly, subconscious control. e.g. heart beat or digestion.
Sympathetic Motor System (part of Autonomic NS)
Flight or fight responses. Neurotransmitter = noradrenaline.
Parasympathetic Motor System (part of Autonomic NS)
Relaxing responses. Neurotransmitter = acetylcholine.
Cerebrum
Controls voluntary actions e.g. learning, personality and conscious thought.
Cerebellum
Controls unconscious functions e.g. posture, balance, non-voluntary movement.
Medulla Oblongata
Used in autonomic control e.g. heart and breathing rate.
Hypothalamus
Regulatory centre for temp. and water balance.
Pituitary Gland
Stores and releases hormones that regulate many body functions.
Reflex Arc
Receptor - detect stim and create AP in sensory.
Sensory - carry impulse to spinal cord.
Relay - connect sensory to motor within spinal cord or brain.
Motor - carry impulse to effector.
Effector - carry out appropriate response.
Knee-jerk Reflex
Spinal reflex (brain not involved). Tap patella (stim), initiate arc (causes leg to kick).
Blinking Reflex
Cranial reflex (spine not involved). Involuntary, cornea stim. Keep cornea from damage from foreign objects. Also due to loud noise or bright light.
Reflexes inc. survival chance by…
Being involuntary.
Not having to be learnt.
Extremely fast.
Everyday actions (staying upright/digestion).
Skeletal Muscle
Make up bulk of body muscle tissue. Responsible for movement e.g. biceps/triceps.
Cardiac Muscle
Only in the heart. Myogenic (contract without nervous stim, causing regular rhythmed heart beat).
Involuntary Muscles (aka Smooth Muscle).
Walls of hollow organs e.g. stomach/bladder and wall of blood vessels and digestive tract (move food along gut).
Structure/Function: Skeletal Muscles.
Striated.
Conscious.
Regularly arranged so muscle contracts in one direction.
Rapid & short contraction.
Structure/Function: Cardiac Muscles.
Striated.
Involuntary.
Cells branch/interconnect, result in simultaneous contraction.
Intermediate contraction.
Structure/Function: Smooth Muscles.
Non-striated.
Involuntary.
Non regular arrangement (diff cells contract in diff directions).
Slow & long lasting contraction.
