Nervous System Flashcards
What are nerves
They detect changes in our environment (stimuli) through cells called receptors
What are receptors
Things sensitive to things such as light, pressure and chemicals in the air
Examples of receptors
Chemoreceptors
Thermoreceptors
Mechanoreceptors
Photoreceptors
What do chemoreceptors detect
Chemicals
What do thermoreceptors detect
Heat
What do mechanoreceptors detect
Pressure
What do photoreceptors detect
Detective light
What is a pancinian corpuscles
Type of mechanoreceptor
Respond to changes in pressure
Found deep in skin in feet, fingers. External genitalia and in our joints
What is a neurone
A cell which carry’s Information to and from the central nervous system in the form of electrical impulses called action potentials
What are the 3 types of neurones and the order they are in
Sensory
Relay
Motor
Where are the neurones used in the stimulus - response system
Stimulus
Receptor
— SENSORY NEURONE
Coordinator — RELAY NEURONE
— MOTOR NEURONE
Effectors
Response
What is the Axon of a neurone
Long process carries impulses (action potential) away from cell body, often over a long distance
What is the cell surface membrane of a neurone
Gated ion channels controlling movement of Na+ K+ ions
What is the cell body of a neurone
Contains the nucleus, many mitochondria and ribosomes
What is the dendrites in the neurones
Small processes connecting to other neurones carrying nerve impulses towards the cell body
What is the Schwann cells in the neurone
Wrap around the axon of 30% of sensory and motor neurones, these cells form a fatty insulating layer of myelin
What is the myelin sheath in the neurone
Insulates so prevents ion movement resulting in increase speed of conduction as impulse ‘jumps’
What are the nodes of Ranvier in the neurone
Short gaps ( about 2-3mm long ) between the Schwann cells occur every 1-3 mm, non myelinated
What is action potential
When a stimulus is detected by a sensory receptor, the energy of the stimulus temporarily reverses the charges on the axon membrane .
What does the resting potential of the axon membrane look like
+++++++++. Positive charge
___________
————— Negative charge
___________
+++++++++ positive charge
What are the Oder of the process in action potential
Depolarisation
Repolarisation
Hyperpolarisation
Explain depolarisation in action potential
Sodium voltage gated channels open and Na+ rush in causing more sodium gates to open changing the charge from negative to positive reaching +40mV . This is known as generator potential.
Explain Repolarisation in action potential
Sodium voltage gated channels have shut and Voltage gated potassium ion channels open and k+ diffuse out
Explain Hyperpolarisation in action potential
There’s an overshoot in membrane potential as to much K+ leave.
Sodium-Potassium pump open to allow membrane to return to its resting potential. (Sodium leave and potassium move in)
What is a synapse
A connection between adjacent neurones
What are the 2 types of synapses ( you only need to know one )
Chemical
Electrical ( don’t need to know )
What is the cholinergic synapse
A neurotransmitter
ACh ( acetylcholine )
What is the enzyme that hydrolysis ACh and is found in the cleft in a synapse called
Acetylcholinesterase
How does transmission occur across a chemical synapse ( detailed )
1 Action potential arrives at the end of the presynaptic membrane
2 Calcium ion channels in the synaptic knob open
3 Calcium ions enter the synaptic knob
4 Synaptic vesicles containing neurotransmitter fuse with the presynaptic membrane
5 Acetylcholine is released into the synaptic cleft
6 Acetylcholine fuses with receptor sites on the sodium ion channel
7 There is an influx of sodium ions into the postsynaptic neurone down a concentration gradient triggering a new action potential
8 Acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid which diffuses back into the presynaptic neurone
9 ATP released by mitochondria recombine choline and ethanoic acid into acetylcholine which is stored in synaptic vesicles for future use
10 Sodium ion Channels close
What does unidirectionally mean in synapses
Nerve impulses travel in one direction
Vesicles in presynaptic neurone only ( receptors on postsynaptic)
Summation , temporal and spatial in synapses
Temporal = time
Spatial = more than one neurone
Inhibition in synapses
Some pre-synaptic neurones can produce inhibitory post synaptic potentials
Prevent an action potential in the post synaptic neurone or reduce the effect of summation
Habituation in synapses
Synapse fatigue
No neurotransmitter available after repeated stimulation so neurone can no longer respond to a stimulus (why we get used to a smell or background noise)
What are sensory receptors
Groups of specialised cells which detect changes in the environment
Where are sensory receptors often located
Ear , eye , skin, nose , tongue
How do sensory receptors briefly work
They convert the stimulus detected into a nerve impulse .
The info is then passed through the nervous system to the central nervous system (CNS)
The brain then coordinates the required response and sends an impulse to an effector to get the desired response.
2 features of a sensory receptor
Are specific to a single type of stimulus
They act as a transducer- they convert a stimulus into a nerve impulse
What type of specific receptor is found in the skin and what’s it stimulus
Skin = mechanoreceptor(pacinian corpuscle) = pressure
What type of specific receptor is found in the nose and what’s it stimulus
Nose= chemoreceptor ( olfactory receptor) = chemicals
What type of specific receptor is found in the tongue and what’s it stimulus
Tongue= thermoreceptor (end bulbs of Krause) = heat
What type of specific receptor is found in the eye and what’s it stimulus
Eye= photoreceptor (cone cell) = light
What is a pacinian corpuscle and where is it located
A specific sensory receptor
Detect mechanical pressure
Mainly located deep within your skin in the fingers and soles of the feet . Also found within joints (so you know which joints are changing direction.
Brief idea of how the pacinain corpse works
Has special sodium channel called a stretch-mediated sodium channel.
When channel changes shape, their permeability to sodium also changes .
How a pacinian corpscle converts mechanical pressure into a nervous impulse (detailed)
1 In its resting state, the stretch-mediated sodium ion channels in the sensory neurones membrane are too narrow to allow sodium ions to pass through them
2 When pressure is applied to the pacinian corpuscle the corpuscle changes shape. This causes the membrane surrounding its neurone to stretch
3 When the membrane stretches, the sodium ion channels present widen. Sodium ion can now diffuse into the neurone
4 The influx of positive sodium ions changes the potential of the membrane - it becomes depolarised. This results in a generator potential
5 In turn, the generator potential creates an action potential ( a nerve impulse) that passes along the sensory neurone
What is the receptor in the nervous system
Detects the stimulus and converts the energy of the stimulus into an electrical impulse (acts as a transducer)
What is the sensory neurone in the nervous system
Carries the nerve impulse from the receptor to the CNS
What is the motor neurone in the nervous system
Carries the nerve impulse from the CNS to the effectors
What is the impulse in the nervous system
Mechanism of conducting the action potential along the length of a nerve axon. Wave of depolarisation
What is the CNS in the nervous system
Central part of the nervous system, consists of the brain and spinal cord
What is the PNS in the nervous system
The sensory and motor neurones connecting the sensory receptors and effectors to the CNS
What is the Autonomic nervous system
Division of the nervous system that coordinates internal organs, smooth muscle and glands - involuntary body functions
What is the Somatic nervous system
Part of the peripheral nervous system (PNS), coordinates voluntary control of skeletal muscles
What is the Parasympathetic nervous system
Branch of the autonomic nervous system that relaxes your body
What is the Sympathetic nervous system
Branch of the autonomic nervous system that stimulates the body e.g. fight or flight response
What is the cerebral cortex in the brain
Sensory information such as vision , smell and hearing processed here. Higher cognitive functions
What is the hypothalamus in the brain
Homeostasis: control of body temperature and osmoregulation . Secretes hormones
What is pituitary Gland in the brain
Produced hormones that control growth, sexual development and metabolism
What is the cerebellum in the brain
Fine motor control, posture and balance
What is the medulla oblongata
Controlled breathing , heart rate and blood pressure ; reflex actions such as vomiting and sneezing
What is the corpus callosum in the brain
Connects the left and right hemisphere to coordinate information
What are the steps between the stimulus and response for a reflex
Receptor - detects stimulus and creates an action potential in the sensory neurone
Sensory neurone - carries impulse to spinal cord
Relay neurone - connects the sensory neurone to the motor neurone within the spinal cord or brain
Motor neurone - carries impulse to the effector to carry out the appropriate responce
What is the spinal cord
It is a column of nervous tissue running up the back . It is surrounded by the spine for protection. At intervals along the spinal cord pairs of neurones emerge.
What are 4 reflex examples and what type of reflex they are and why
Blinking - cranial (brain) reflex , close eyes loud sounds , sudden movements close to eye
Corneal - cranial (brain) reflex , object touching eye
Optical - cranial (brain) reflex , sudden bright light
Knee jerk - spinal reflex , coordination, balance
How does the coordination of fight or flight work
1 sensory centres in the cerebrum process these sensory inputs
2 signals are passed to the association centres
3 The cerebrum stimulates the hypothalamus if the threat is recognised
4 the hypothalamus increases activity of the sympathetic nervous system stimulating release of hormones from the anterior pituitary gland.
How many beats does the human heart do aprox per minute at rest
70 beats p m
What is the heart rate controlled by
Autonomic nervous system/ medulla oblongata
How does the medulla control the heart rate
It is linked to the SA node by motor neurones
There are 2 receptors in the blood which detect changes to increase or decrease heart rate what are the receptors called and what to they detect
Baroreceptors - blood pressure
Chemoreceptors - CO2 concentration
What is the SAN
SA node
A pacemaker
Sends a wave of electrical activity over atrial walls so that both atria contract at same time
What is the AVN
AV node
Causes ventricles to contract from both up by sending impulses through purkyne fibres (bundle of His)
