Nervous System Flashcards
What are the divisions of the nervous system?
2 types of nervous tissue
Neurons and neuroglia
Neuron
Nerve cell that transmits electrical signals
Structure and functions of the nervous system
- S = CNS (brain and spinal cord) and PNS (cranial and spinal nerves), 2 types of nervous tissue= neurons and glia
- F = receive sensory (afferent) signals, interpret info and coordinate a motor (efferent) response, maintain homeostasis
3 types of neurons
Sensory, motor, interneurons
What is A and what is its structure and function?
Dendrite
- Branched extensions of cell body that receive input from other neurons and transmit towards cell body
What is B?
Cell body
What is G and what is its function?
Nucleus
- Structure within the cell body that contains DNA to control functioning of the neuron
What is C and what is its function?
Axon
- To transport signals from the dendrite to the axon terminals
What is I and what is its function?
Schwann cell
- Glial cell that provides myelin insulation to neurons in PNS
What is H and what is its function?
Myelin sheath
- Fatty covering that insulates the axon and increases the speed of transmission
What is D and what is its function?
Node of Ranvier
- Gaps between Schwann cells in myelin sheath that allow for rapid depolarisation of the impulse
What is F and what is its function?
Axon terminal
- Branch-like extensions of the axon that carry messages from axon to terminal buttons
What is E and what is its function?
Terminal buttons
- Release neurotransmitters to other neurons between the synapse
Name the stages of an action potential
Resting, depolarisation, repolarisation, hyperpolarisation
Describe the resting phase of an action potential
Neuron not responding to stimulus, Na+ and K+ channels closed, SOAPI PONI (sodium outside and potassium inside, positive outside negative inside)
Describe the depolarisation stage of an action potential
- Neurotransmitters binding to receptors on dendrites causes opening of Na+ channels > Na+ ions rush in
- Charge of cell increases (depolarisation), and if threshold is reached, action potential fires
- Charge of cell will continue to increase, eventually becoming positive due to a high concentration of Na+ ions
Describe the repolarisation/hyperpolarisation stage of an action potential
K+ channels open and K+ ions rush out > cell charge decreases (repolarisation) and eventually goes below the resting level (hyperpolarisation), before returning to resting phase
Structure and function of a synapse
- S = space between two neurons where the presynaptic axon connects with the postsynaptic dendrite
- F = allows for transmission of electrochemical messages between neurons
What happens at a synapse?
- Action potential arrives at axon terminals
- Triggers release of neurotransmitters which diffuse across synapse and bind to specific receptors on target cell
- Target cell is activated or inhibited
What is a neuromuscular junction
Where a nerve joins with an effector muscle
Structure and function of a neurotransmitter
- S = chemical messenger released by the axon of a presynaptic nerve. Binds to a specific receptor of a postsynaptic nerve or effector muscle
- F = transmit signals from presynaptic nerve to post-synaptic nerve or effector muscle
Examples of neurotransmitters
Acetylcholine (Ach), endorphin, dopamine, epinephrine (adrenaline)
2 types of neural messages
- Within neurons: electrical (action potential)
- Between neurons: chemical (neurotransmitters)
What are glia?
Supportive/connective cells of the nervous system > do not transmit an action potential
Types of glia
- CNS: astroglia, microglia, oligodendroglia
- PNS: satellite cells, schwann cells
Astroglia
Star-shaped cells that provide physical and nutritional support for neurons and clean up brain debris in CNS
Microglia
Digest parts of dead neurons in CNS
Oligodendroglia
Provide myelin insulation to neurons in CNS
Satellite cells
Provide physical support to neurons in PNS
What are the 2 main divisions of the nervous system and what are their components?
- CNS: brain and spinal cord
- PNS: peripheral nerves (cranial and spinal)
Structure and function of the CNS
- S = brain and spinal cord
- F = to process info received from internal and external stimuli
Structure and function of the brain
- S = mass of soft nerve tissue, located within the cranial cavity
- F = receives and interprets sensory information to coordinate a motor response
Grey vs white matter
- Grey: neuron cell bodies, axon terminals and dendrites (therefore neurotransmitters) - on outside of brain and inside of spinal cord
- White: axons surrounded by myelin sheath - on inside of brain and outside of spinal cord
3 main sections of the brain
Cerebrum, cerebellum, brain stem
Structure and functions of the cerebrum
- S = soft nerve tissue divided into L and R hemispheres, connected by corpus callosum. 4 lobes= temporal, parietal, frontal, occipital
- F = coordination of movement, vision, hearing, emotions, problem solving, learning etc
3 layers of protection for the brain
Cranium, meninges, CSF
Structure and function of meninges
- S = multi-layered membrane surrounding the brain and spinal cord (dura mater is most superficial, then arachnoid and pia mater)
- F = to protect the brain and spinal cord
Structure and function of CSF
- S = colourless fluid surrounding the brain and spinal cord containing chemicals e.g. salts/glucose/proteins dissolved in water located between the pia and arachnoid mater
- F = to protect the brain and spinal cord by cushioning, circulates nutrients and waste to and from brain, maintains pressure
What is the function of the hypothalamus?
Maintain homeostasis e.g. temp, fluid balance, appetite, sleep cycles etc by controlling secretion of hormones from pituitary gland
Motor cortex vs somatosensory cortex
- Motor: coordinates motor output, located in frontal lobe
- Somatosensory: receives sensory input, located in parietal lobe
What is A and what is its function?
Frontal lobe
- Thinking, problem solving, personality, emotions, voluntary movement of skeletal muscles
What is B and what is its function?
Parietal lobe
- Sensory info from skin, perception, spelling, arithmetic
What is C and what is its function?
Occipital lobe
- Vision, processing colour, shape, perspective
What is D and what is its function?
Cerebellum
- Receive sensory info from inner ear, eyes, muscles and then coordinate voluntary muscle movement, allowing muscles to make adjustments to maintain balance and equilibrium
What is E and what are its 3 functions?
Brain stem (3 sections = midbrain, medulla oblongata, pons)
- Conduction of signals from spinal cord to brain and vice versa
- Contains control centres for vital body functions e.g. respiration, vasomotor centre, cardioregulatory centre etc
- Other autonomic functions e.g. digestion, salivation, urination
What is F and what is its function?
Temporal lobe
- Memory, language, hearing, understanding
What is the structure and function of the spinal cord?
Spinal cord
- S = long tubular structure that connects the brain to the rest of the body, located within the vertebral column
- F = transmits sensory info from body to brain and motor info from brain to body
3 layers of protection for the spinal cord
Vertebrae, meninges, CSF
Divisions of spinal nerves
- Cervical (8)
- Thoracic (12)
- Lumbar (5)
- Sacrum (5)
- Coccyx (1)
Cauda equina
Bundle of nerves extending beyond the spinal cord, carries nerve impulses to and from legs (looks like a frayed rope)
2 roots of spinal nerves
- Ventral/motor root: carries motor signals from CNS to body (particularly skeletal muscles)
- Dorsal/sensory root: carries sensory signals from body to spinal cord
What are A, B and C?
- A = dorsal root (sensory)
- B = grey matter
- C = dorsal horn (sensory)
What are D, E and F?
- D = ventral root (motor)
- E = white matter
- F = ventral horn (motor)
Dermatome
An area of skin whose sensory nerves all come from a single spinal nerve root
Structure and function of the PNS
- S = all nerves outside the CNS (cranial, spinal and peripheral nerves)
- F = carries sensory information from the body to the CNS and motor information from the CNS to the body
Structure and function of cranial nerves
- S = 12 pairs, connect brain to head, neck and trunk, part of PNS
- F = smell, sight, eye movement, sensation in face, hearing, balance, swallowing
Structure and function of spinal nerves
- S = 31 pairs, connect the spinal cord to other organs and parts of the body
- F = sends sensory and motor signals between the CNS and the PNS to coordinate activities e.g. movement
What are the two divisions of the PNS and what does each control?
- Autonomic: involuntary activities e.g. HR, RR, peristalsis
- Somatic: voluntary skeletal muscle contractions
What are the 3 divisions of the autonomic nervous system and what does each control?
- Sympathetic: fight/flight: decreased digestion, increased HR, dilation of pupils, diversion of blood to muscles which need it more, lack of bladder control, goosebumps
- Parasympathetic: rest & repair after fight/flight: increased digestion, decreased HR, constriction of pupils, return of bladder control etc
- Enteric: coordinates function of GI tract
What is a reflex?
Involuntary and almost instantaneous movement in response to a stimulus, often spinal reflexes (bypass the brain = rapid), role in survival (protect from hazards etc)
What is a reflex arc?
- Path taken by nerve impulses in a reflex
- Receptor > sensory neuron > interneuron > motor neuron > effector
Monosynaptic vs polysynaptic reflex and give e.g.s
- Monosynaptic: one synapse = sensory > motor e.g. patellar and achilles reflex
- Polysynaptic: multiple synapses = sensory > inter > motor e.g. withdrawal response
Describe the patellar reflex
Receptors detect force of hammer, sensory neuron transmits signal to a motor neuron in spinal cord, activating only one synapse therefore rapid knee jerk reflex
Describe the withdrawal reflex
- Stimulus detected by sensory receptors
- Sensory neurons transmit info via sensory (afferent) pathway to spinal cord
- Interneurons in spinal cord initiate involuntary motor movement
- Motor neurons transmit info via motory (efferent) pathway to muscles
- Muscles perform withdrawal reflex response w/o input from brain
What are primitive reflexes and give some e.g.s
- Reflexes that originate in the CNS
- Normal in infants but abnormal in adults as they are suppressed by the development of the frontal lobes
e.g. Moro (startle), Babinski (foot tickle), grasp
How to maintain a healthy nervous system
- Get enough sleep to help consolidate neural pathways and allow the mind to rest. Sleep also reduces blood pressure, decreasing the risk of stroke
- Eat a balanced diet with plenty of fibre and nutrients, low in fats and salts to reduce the risk of stroke
- Avoid excessive alcohol or drug intake as they can interfere with brain activity
What is a stroke and what are the 2 types?
Damage to the brain from interruption of its blood supply, resulting in a lack of oxygen to brain tissue (ischaemic or haemorrhagic)
Risk factors for stroke
Smoking/obesity/high salt diet > high BP > atherosclerosis/weakening of blood vessel walls > stroke
Ischaemic vs haemorrhagic stroke
- Ischaemic: blockage in blood vessels e.g. blood clot/atherosclerosis that supply brain > lack of O2
- Haemorrhagic: blood vessel supplying brain bursts due to high BP causing bleeding in the brain
What is a concussion and what are the symptoms?
- A form of mild TBI where the brain comes into contact with the cranium, caused by a direct or indirect blow to the head
- Sx (depend on what part of the brain is affected): headache, confusion, dizziness, blurred vision, nausea etc
What is MS?
Multiple Sclerosis
- Autoimmune disease where autoantibodies destroy the myelin sheath of neurons, causing sclerosis (hardening) > slowed transmission of sensory and motor impulses
What is myasthenia gravis?
- Neuromuscular autoimmune disease resulting in skeletal muscle weakness of eyes, face, swallowing muscles
- Symptoms include diplopia, ptosis (drooping eyelids), dysphasia, difficulty walking
How is myasthenia gravis caused?
- Autoantibodies block Ach receptors at neuromuscular junction > some messages from nerve can’t pass to muscle to initiate contractions > weakness
Ment/o
Neur/o
Mind
Nerve
Encephal/o
Radic/o
Brain
Nerve root
Mening/i,o
Psych/o
Meninges
Mind
Somn/i,o
Dur/o
Sleep
Dura mater
Radicul/o
Cerebr/o
Nerve root
Cerebrum
Cerebell/o
Cephal/o
Cerebellum
Head
Gli/o
Phren/o
Neuroglia
Mind
Esthesi/o
Medull/o
Sensation, feeling
Medulla oblongata
Myel/o
Arthr/i,o
Spinal cord
Speech
Dysarthria
Hypertonia
Abnormal condition of difficulty speaking (not painful joints)
Abnormal condition of excessive muscle tone
Hyperreflexia
Abnormal condition of excessive reflex activity
-asthenia
CSF
Weakness
Cerebrospinal fluid
Ataxia
Loss of control of body movements
TIA
Hemianopia
Transient ischaemic attack
Abnormal condition of no vision in one eye
Neglect
Lack of attention and spatial awareness post-CVA
Hydrocephalus
Excess accumulation of CSF in brain
Ganglion
Collection of nerve cells
