Nervous System Flashcards
What are the structural classifications of the nervous system?
Central NS = brain and spinal cord
Peripheral NS = cranial nerves (12 pairs) and spinal nerves (31 pairs)
What are the functional classifications of the nervous system?
Peripheral NS = Sensory (afferent) and Motor (efferent) neurones
Sensory = senses and sensory receptors
Motor = Somatic and autonomic
Somatic (voluntary) = skeletal muscles
Autonomic (involuntary) = smooth muscle, glands, cardiac muscle
Autonomic = Parasympathetic and Sympathetic
Ganglion
A group of cell bodies in the PNS
Nuclei
A group of cell bodies in the CNS
How many efferent neurones does the neuron pathway, controlled by the divisions of the autonomic motor NS have?
2 efferent neurones
What are the 2 efferent neurones of the parasympathetic and sympathetic NS called?
1) Pre-ganglionic neurone = cell body will be in the CNS (anywhere apart from the cerebellum)
2) Post-ganglionic neurone = will be attached to the effector (smooth muscle, gland or cardiac muscle)
Describe the pre-ganglionic neuron of the sympathetic NS:
Cell body: In the CNS (anywhere but the cerebrum)
Axon: Extends down the anterior grey column of the spinal cord and terminates at the spinal cord between T1 and L2
Synapses with the cell body of the post-ganglionic neurone: Either in the lateral chain of sympathetic ganglia or the prevertal chain of sympathetic ganglia)
What is the neurotransmitter at the synapse between the pre-ganglionic neurone and the post-ganglionic neurone of the sympathetic NS?
ACETYLCHOLINE
Does the pre-ganglionic sympathetic neurone always synapse with the post-ganglionic neurone at the same level is terminated the spinal cord?
No it can either be on the same level or not
How does the pre-ganglionic axon of the sympathetic NS reach the prevertal chain of ganlia?
It must pass the lateral chain of ganglia before reaching the prevertal chain
Describe the post-ganglionic neurone of the sympathetic NS?
Cell body: In the lateral chain or prevertal chain of sympathetic ganglia
Axon: Attached to the effector
What is the neurotransmitter at the post-ganglionic neurone of the sympathetic NS?
Noradrenalin (however, can sometimes be acetylcholine)
Why does the post-ganglionic neurone of the sympathetic NS sometimes release acetylcholine at the synapse?
This will occur at effectors that are only supplied by the sympathic post-ganglionic neurones (Skin, sweat glands and skeletal muscles) and so ‘parasympathic’ effects can not occur.
These effectors contain NICATINE-ACETYLCHOLINE RECEPTORS - that bind to the acetylcholine from the post-ganglionic sympathetic neurones (in order for parasympathetic effects to occur)
Describe the pre-ganglionic neurones of the parasympathetic NS?
Cell body: In the CNS (anywhere but the cerebrum) or in the spinal cord
Axon: Extend down in the grey anterior column of the spinal cord and terminates the spinal cord at 2,3 or 4 sacral region.
Synapses: With the post-ganglionic neurone either in the ganglion or the effector wall
What neurotransmitter is at the synapse of the parasympathetic pre-ganglionic neurone and the post-ganglionic neurone?
ACETYLCHOLINE
Describe the post-ganglionic neurones of the parasympathetic NS?
Cell body: Ganglion or inside effector
Axon: Terminate with the effector
What neurotransmitter is at the synapse of the parasympathetic post-ganglionic neurone and the effector?
ACETYLCHOLINE
What receptors do the effectors (that are supplied by post-ganglionic parasympathetic neurones) have?
Either:
1) Nicotine-acetylcholine receptors (parsympathetic and can be sympathtic - skin, sweat glands and smooth muscles)
2) Muscarine-acetylcholine receptors (only parasympathetic)
Differences between the pre-ganglionic and post-ganglionic axons of the sympathetic and parasympathic neurones:
Sympathetic:
Pre-G: long
Post-G: short
Parasympathic
Pre-G: short
Post-G: long
What are the functions and type of reactions of the sympathetic NS?
Fight and flight
Catabolic (releases energy) reactions
What are the functions and type of reactions of the para-sympathetic NS?
Rest and Digest
Anabolic (stores energy) reactions
What are the 3 major anatomical regions of the brain?
1) Cerebrum (and lobes of the cerebral hemisphere)
2) Brain Stem (Midbrain, Pons and Medulla Oblongata)
3) Cerebellum
Cerebrum is divided into?
2 cerebral hemispheres
What joins together the 2 cerebral hemispheres?
CORPUS CALLOSUM
What are the 2 cerebral hemispheres divided into?
Lobes of the cerebral hemisphere
Why are the lobes of the cerebral hemisphere called what they are called?
The names will be associated with the bones of the cranium under which they live.
Where are the cell bodies and nerve fibres found in the brain?
Cell bodies = surface (grey matter)
Nerve fibres = inside (white matter)
What are the 4 main cerebral lobes?
1) Frontal lobe
2) Parietal lobe
3) Temporal lobe
4) Occupital lobe
What 3 sulcus’ separate the cerebral lobes?
1) Central sulcus (between the frontal and parietal lobe)
2) Lateral sulcus (between the frontal and the temporal)
3) Parietal - occupital sulcus (between the parietal and occupital lobe)
What areas are contained within each other 4 main cerebral lobes?
1) Frontal lobe: Motor speech area, pre-motor area and motor area
2) Parietal lobe: Sensory area, taste area and sensory speech area
3) Temporal lobe: Auditory area and olfactory area (deep within)
4) Occupital lobe: Visual area
Describe the higher motor neurones of the motor area?
Cell bodies: In the cerebral cortex (grey matter)
Axons: Pass through the internal capsule, cross over to the other side in the medulla oblongata and synapse at the appropriate level of spinal cord.
Why do the upper motor neurones cross over at the medulla oblongata?
Because the cells bodies of the upper motor neurones in the motor area control movements of the opposite side of the body to the hemisphere they are positioned in.
So left control right side of the body movements (visa versa)
Cell bodies of the upper motor neurones, positioned at the upper areas of the motor area control:
The lower parts of the body - feet
Cell bodies of the upper motor neurones, positioned at the lower areas of the motor area control:
The upper parts of the body - face, arms, hands
Describe the lower motor neurones of the motor area?
Axons are attached to skeletal muscle and the cell bodies of lower motor neurones will initiate voluntary actions
If a voluntary action is more complex how does this affect the amount of cell bodies in the cerebral motor area?
The more complex the voluntary action - the more cell bodies in the motor area control this action
What is the function of the pre-motor area?
The cell bodies in the premotor area of the cerebral cortex will exert a controlling force on the cell bodies in the motor area of the cerebral cortex.
So, the skeletal muscle movements that they control occur in an orderly fashion
What is the function of the motor speech area?
The cell bodies in the motor speech area of the cerebral cortex will exert a controlling force on the cell bodies in the motor area of the cerebral cortex that control the skeletal muscles that are involved in speech.
What is the function of the frontal area?
The frontal area is a highly developed area compared to other animals.
It communicates will all the cell bodies in the cerebral cortex in order to control:
1) Character
2) Behaviour
3) Emotional state
If the body part sends more sensory input to the cerebral cortex…
The more area the cell bodies of the cerebral cortex of the sensory areas will be taken up in order to interpret the information from this body part
What is the function of the parietal area?
Obtain and retains information about objects. It is because of this area that people are able to detect objects by touch.
What is the function of the sensory speech area?
Interprets spoken words. The dominent sensory speech area will be in the opposite cerebral hemisphere, to the hand you write with
What is the function of the auditory area?
Interprets information sent from the inner ear
What is the function of the taste area?
Interpret information sent from the nerve endings situated in: tongue, pharynx, cheeks and paletes
What is the function of the visual area?
Interprets information sent from the 2nd cranial nerve
What is the function of the olfactory area?
Interpret informaion sent from the 1st cranial nerve
What is the name of the 3 nuclei in the cerebrum which act as relay neurones?
1) Basal Nuclei
2) Thalmus
3) Hypothalamus
What is the function of the basal nuclei?
By controlling muscle tone in order to carry out slow and co-ordinated activites
What is the function of the thalmus?
Sensory afferent neurones will pass through the thalmus before being redistributed to the appropriate areas of the cerebral cortex.
What is the function of the hypothalamus?
Stimulates or inhibits the release of hormones from the anterior and posterior pituitary gland. As it is connected to the a and p pituitary gland by:
Anterior - by blood vessles
Posterior - by nerve fibres
What does the midbrain contain, connect and act as a relay station for?
Contains: nerve fibres and cell bodies
Connect: connects the cerebrum with lower parts of the brain and the spinal cord
Relay station for: ascending and descending nerve fibres
What does the pons contain, connect and act as a relay station for?
Contains: Mainly nerve fibres
Connect: 2 cerebral hemispheres
Relay station for: ascending and descending nerve fibres
What does the medulla oblongata contain, control and act as a relay station for?
Contains: Mainly nerve fibres
Controls: Autonomic reflex activities
Relay station for: afferent/sensory nerve fibres will pass the medulla oblongata before reaching the cerebrum
What autonomic reflexes does the medulla oblongata control?
1) Respiratory reflexes
2) Cardiac reflexes
3) Vasomotor reflexes
4) Other reflexes including: swallowing, coughing, vomitting, sneezing
What is the other special features of the medulla oblongata?
Upper motor neurones will cross to the other side in the medulla oblongata
How are the nerve fibres and cell bodies arranged in the pons and medulla oblongata?
The cell bodies (grey matter) are central and the nerve fibres (white matter) are around the surface.
What is the function of the cerebellum?
It INVOLUNTARY controls VOLUNTARY muscular movements. In doing so it maintains balance and posture.
How does the cerebellum carry out its function?
By receiving PROPRIOCEPTOR impluses from:
Eyes and ears: gives information about the position of the head in space.
Muscles and joints: gives information about the positions of muscles and joints in relation to the rest of the body
Where does the spinal cord extend from and where does it end?
The spinal cord extends from the medulla oblongata down to the 1st Lumbar vertebrae.
Where is cerebral spinal fluid taken from during a lumbar puncture?
2nd lumbar puncture downwards
Describe the arrangement and number of nerve pairs in the brain?
Cranial nerve pairs: 7 Thoracic nerve pairs: 12 Lumbar nerve pairs: 5 Sacral nerve pairs: 5 Coccygeal nerve pairs: 4
Describe the arrangement of nerve fibres and cell bodies in the spinal cord?
(opposite arrangement to the brain) Nerve fibres (white matter) = outside Cell bodies (grey matter) = inside
What is the grey matter of the spinal cord split up into and what cell bodies do they each contain?
Anterior grey column: Cell bodies of lower motor neurons and inter-neurones
Posterior grey column: Cell bodies of sensory neurones (that receive impulses from the circumference of the body)
What are the names of the 3 meninges that surround the brain and spinal cord (and the spaces inbetween)?
(brain-skull) 1) Pia Mater (Sub- arachnoid space) 2) Arachnoid mater (Sub-dural space) 3) Dura mater
How to describe the pia mater?
fine, connective tissue surrouning the brain and spinal cord
How to describe the dura mater?
A double layer of dense, fibrous tissue
What does the epidural space separate?
The epidural space separates the spinal vertebrae from the ligaments.
Production of cerebral spinal fluid?
The brain is split into 4 ventricles. The walls of the ventricles contain blood vessels.
CHOROID PLEXUSES = an area of blood vessels in the ventricle walls that secrete CSF.
What are the 7 things contained in CSF?
1) Water
2) Salt
3) Glucose
4) Plasma proteins
5) WBC’s
6) Urea
7) Creatinine
What are the 5 functions of CSF?
1) Protects brain and spinal cord
2) Acts as a shock absorber for the brain and spinal cord
3) Maintains the pressure within the brain and spinal cord
4) Keeps brain and spinal cord moist
5) Transfer of substances between brain/spinal cord and nerve fibres.
Which space is the cerebral spinal fluid contained in?
Subarachnoid space
Describe the process for the circulation of the cerebral spinal fluid?
1) The CSF is released from the choroid plexuses in the ventricle walls of the brain.
2) It travels across the pia mater and into the subarachnoid space.
3) It will be taken up by the ARACHNOID VILI in the arachnoid mater.
4) It will return to the blood as it flows to the VENOUS SINUS in the dura mater.
Which ventricle of the brain contains the choroid plexus that releases cerebral spinal fluid that will circulate around the brain and spinal fluid?
4th ventricle.
What 3 characteristics make a neurone unique?
1) Can’t reproduce
2) Irritability - it can initiate an action potential
3) Conduction - it can transfer an action potential along its length
What are the 5 steps of an action potential and what is the voltage at each step?
1) Resting potential (-70mV)
2) Depolarisation (Theshold = -50mV and AP= +40mV)
3) Repolarisation (-70mV)
4) Hyperpolarisation (-80mV)
5) Repolarisation (-70mV)
The resting potential (-70mV):
Membrane is polarised. The resting potential is maintained due to the Na+K+ATPase pump pumping 3 sodium out of the membrane and 2 potassium into the cell. As more positive are being pumped out the membrane is negative.
In order for the ions to be available to do this. Sodium and potassium LEAK across sodium and potassium channels along their concentration gradients.
Depolarisation:
1) When the (stimulus)-gated sodium channels have been stimulated, they will open to cause sodium reflux into the neuron.
2) If the stimulus was strong enough, the sodium reflux will cause the membrane potential to reach -50mV (threshold).
3) This causes the voltage-gated sodium channels to open and cause an even greater influx of sodium.
4) The membrane potential is now +40mv (action potential)
5) The action potential is propagated along the axon length as neighbour voltage-gated sodium channels open and so on (positive feedback)
How does an action potential only occur in 1 direction?
The voltage-gated sodium channels need a REFRACTORY PERIOD before they open again.
Repolarisation:
1) The voltage-gated potassium channels behind the propagation of the action potential (upstream) open.
2) Potassium is pumped out of the membrane.
3) More positive ions are pumped out - causing the membrane potential to drop back to -70mV.
Hyperpolarisation:
1) The voltage-gated potassium channels pump too many potassium out of the membrane.
2) This makes the membrane more negative than resting potential (-80mV).
Repolarisation:
1) The voltage-gated potassium channels close.
2) The Sodium-potassium ATPase pump restores resting potential by pumping 3 sodium out and 2 potassium in again.
3) Membrane potential returns to -70mV.
What 2 factors does the movement of ions across the axon membrane depend on?
1) Voltage = Positive are attached to negative (visa versa)
2) Concentration gradient = high conc. to low
What causes a strong electrochemical gradient
Where there is a high concentration of positive ions and a low concentration of negative ions (v/v).
What are the 3 properties of an action potential?
1) All the same size (due to refractory period)
2) One direction (due to refractory period)
3) The strength of the action potential is conveyed by the frequency of the action potentials.
3 factors that affect action potential propagation along the axon?
1) Temperature: affects the kinetic energy of the sodium ions which will affect the diffusion rate.
2) Axon diameter: wider = faster diffusion rate
3) Myelinated/non-myelinated axon: If myelinated, SALTATORY PROPAGATION will occur and sodium influx will only occur at the Node of Ranvier as the myelin sheath acts as an electrical insulator
How do nerve impulses stop in multiple sclerosis?
1) The body’s own immune system attacks the myelin sheath and breaks it down.
2) Sodium influx will still only occur where once previously the Node’s of Ranvier were.
3) The sodium is too far apart to stimulate other voltage-gated sodium channels to open
4) The action potential can not be propigated along the length of the axon
Where are the cell bodies found in sensory neurones?
Cell body is on the outside
What are the 6 main peripheral receptors called?
1) Chemoreceptors
2) Mechanoreceptors
3) Osmoreceptors - osmolarity
4) Proprioreceptors - position
5) Baroreceptors - pressure
6) Thermoreceptors - temperature
Is there a pre-ganglionic and post-ganglionic neurones in the somatic neurone pathway that control skeletal muscles.
NO! - their is one neurone that carry impulses directly to the skeletal muscle (acetylcholine is the neurotransmitter)
2 common excitatory neurotransmitters?
1) Noradrenalin
2) Acetylchloline
5 common inhibitory neurotransmitters?
1) Dopamine
2) Endophins
3) Glutamine
4) GABA
5) Serotonin
What is the sequence of events at the synaptic cleft which causes an action potential to be initiated n the post-synaptic neurone?
1) The action potential arrives at the pre-synaptic neurone.
2) Voltage-gated calcium channels open.
3) Influx of calcium.
4) This stimulates the synaptic vesicles to bind to the pre-synaptic membrane.
5) By EXOCYTOSIS, they will release their neurotransmitters into the synaptic cleft.
6) Calcium ions are actively transported out of the pre-synaptic knob.
7) The neurotransmitters bind to chemical-gated sodium channels in the post-synaptic membrane.
8) This will stimulate them to open and sodium influx occurs in the 2nd neurone.
How are the neurotransmitters recycled?
1) Enzymes (e.g. Acetylcholinesterase) will HYDROLYSE the neurotransmitters (either bound or unbound)
2) The breakdown products will be taken back up into the pre-synaptic neurone by ENDOCYTOSIS.
3) These will be used to synthesis new neurotransmitters.
