Nervous System physiology

What is the function of sensory or afferent neurones?

Activated by stimulus and form an action potential in its axon conveying it into the CNS

What is the function of motor or efferent neurones?

Convert action oftentimes away from the CNS to effectors through cranial or spinal nerves

What are the two types of motor or efferent nerves?

Somatic

Autonomic

What is the function of somatic nerves?

Voluntary and reflex skeletal muscle contraction

Contains one neurone travelling directly to the skeletal muscle

What is the function of autonomic nerves?

Involuntary muscle contraction

Contains two neurones

1. preganglionic neurone leaves spinal cord

2. Synapses with postganglionic neurone

3. postganglionic synapses with effector tissue

What is the function of interneurones?

Process incoming sensory information to the CNS and elicit a motor response

What are the functions of the somatic nervous system?

Controls voluntary movements via the skeletal muscles

Involved in reflex arcs and enables conscious actions

What are the functions of the autonomic nervous system?

Controls involuntary reflex activities

What are the two types of nerves involved in the autonomic nervous system?

Sympathetic nerves

Parasympathetic nerves

What is the function of sympathetic nerves?

Prepare the body for action

What is the function of parasympathetic nerves?

Promote rest and recovery

How are action potentials transmitted?

Movment of sodium and potassium ions against the concentration gradient across the nerve cell gradient through protein pumps

How do nerve impulses travel down myelinated axons?

Depolarisation passes along the myelin sheath between nodes, so that the flow of current appears to leap from node to node

What is the name of conduction in myelinated neurones?

Saltatory conduction

What factors determine the speed of conduction?

Diameter of the neurone

Myelinatiom

What is the function of presynaptic neuron?

Cell which sends signal

What is the function of a postsynaptic cell?

Cell that recieves signals

What are the two types of synapses?

Chemical

Electrical

What is the structure of chemical synapses?

Seperated by synaptic cleft filled with interstitial fluid

What is the direction of signal in chemical synapses?

One way

Where are chemical synapses located?

Brain and spinal cord

What is the function of chemical synapses?

Converts electrical signal to chemical and back to electrical

What is an example of function of chemical synapses?

Muscle contraction

What is the structure of electrical synapses?

Connected by gap junctions made of connexons

What is the direction of electrical synapses?

Two way or one way

What is the location of electrical synapses?

Smooth muscle, cardiac muscle and developing embryo

What is the function of electrical synapses?

Synchronises neurone or muscle activity

What is an example of the function of electrical synapses?

Heartbeat coordination

Which is slower; chemical or electrical synapses transmission?

Chemical due to neurotransmitter diffusion

How does peripheral nerve regeneration occur?

Following injury, axon and myelin sheath break down

Muscle connected to nerve weakens

If severed ends are close, neurilemma forms a regeneration tube

Guides growth of new axon fibres, aid from Schwann cells

When is peripheral nerve regeneration impossible?

What might happen instead?

Neurilemma is out of position or destroyed

Sprouting axon and Schwann cells may form tumour like clusters producing severe pain

What are the functions of the cerebrospinal fluid?

Supports and protects

Maintains uniform pressure and acts as a shock absorber

Exchanges nutrients and waste with interstitial fluid

Regulates breathing by bathing medullary surface

What are the three types of functional areas of the brain and what are their functions?

Motor areas for skeletal muscle movement

Sensory areas for receiving sensory impulses

Association areas for implementation mental functions

What is the general trend of the function of anterior area of the cortex?

Motor functions

What is the general trend of the function of posterior area of the cortex?

Sensory functions

What are the nine areas of the cerebral cortex?

Taste

Auditory

Visual

Motor speech

Sensory speech

Prefrontal

Premotor

Primary motor

Somatosensory

What neurones are involved in pathways to skeletal muscles from motor areas of the cerebral cortex?

Upper motor neurone

Lower motor neurone

What is the location of the upper motor neuron?

Passes from motor cortex through internal capsule to medulla oblongata where it crosses to opposite side into spinal cord

What is the location of the lower motor neurone?

Leaves spinal cord into motor end plate of muscle fibre in target muscle

What is the function of the somatosensory area?

Where sensations are felt

What is the function of auditory area?

Recieves signals for hearing

What is the function of the olfactory area?

Impulses from the olfactory epithelium from the nose through olfactory nerves

What is the function of the taste area?

Recieves impulses from sensory receptors in taste buds

What is the function of the pre motor area?

Neurones coordinates and learns movements initiated by primary motor cortex

What is the function of the prefrontal area?

Controls intellectual functions

E.g. emotional management, anticipation of consequences and comprehension of passage of time

What is the function of visual area of the brain?

Where optic nerves from the eye terminate and images are interpreted

Why is rhe visual area found in the occipital lobe?

Protection

Fast, optimised pathway

Specialised processing of colour, motion, depth

What is the function of the sensory speech area of the brain?

Language perception and intelligence

What is rhe function of the parietal-occipital area?

Spatial awareness and language interpretation

What is a functional MRI?

Identifies which regions are active by identifying increased blood flow during specific tasks or mental states

What is rhe function of PET CT?

Introduces a tracer FDG which behaves like glucose which is the main energy store

Active brain region use more glucose and absorb more of the tracer

Tracer collides with electrons to produce detectable gamma rays

What is the function of the thalamus?

Arousal and processing of some emotions and complex reflexes

What are the six functions the hypothalamus controls?

Effectors of autonomic nervous system

Appetite and satiety

Thirst and water balance

Body temperature

Emotional reactions

Circadian rhythms

What is the function of the cerebellum and how does it make it possible?

Coordinated skeletal muscle movements subconsciously by integrating sensory input to maintain posture and balance

What are the four categories of the eye response section of the Glasgow coma scale?

No eye opening

Opens to pain

Opens to speech

Opens spontaneously

What are the five categories of the verbal response section of the Glasgow coma scale?

No verbal response

Incomprehensible sounds

Inappropriate words

Confused but coherent

Orientated and appropriate

What are the six categories of the motor response section of the Glasgow coma scale?

No motor response

Extension to pain

Abnormal flexion to pain

Withdrawal from pain

Localises pain

Obeys commands