Nervous tissue Flashcards
what are myelinated axons surrounded by?
schwann cells
where are unmyelinated axons found?
in the autonomic system and parts of the brain
what does myelin allow?
impulses to travel faster acting as insulation and protection
what is a nerve?
many neurons held together by connective tissue (neuroglia)
what does neuroglia do?
- support neurons physically and metabolically
what are astrocytes?
covers capillaries in brain and helps blood brain barrier
what are oligodendrocytes?
peripheral nervous tissue
what is microglia?
phagocytic cells, part of CNS defence system
what is ependymal?
lining ventricles of brain and central canal of spinal cord
what are three types of neuron?
- unipolar
- bipolar
- multipolar
what forms grey matter?
cell bodies
what forms white matter?
nerve fibre
what are three classes of neurons?
- afferent
- efferent
- interneurons
what does afferent mean?
- sensory - messages towards brain and spinal cord
what does efferent mean?
- motor - messages away from brain and spinal cord
what does interneurons mean?
- message transmission within brain and spinal cord
what is a terminal button?
enlarged end of an axon which has lots of mitochondria
what are the transmitter substances in the peripheral nervous system?
acetyl choline and nor-adrenalin
what is the transmitter substance in the central nervous system?
acetyl choline
what is the post-transmission period called?
refractory period
what are the two components to the central nervous system?
brain and spinal cord
what are the three main divisions of the brain?
- forebrain
- midbrain
- hindbrain
what are the three ares of the forebrain?
- cerebrum
- thalamus
- hypothalamus
what is the cerebrum and what does it do?
- 2 halves separated by longitudinal sulcus
- receive and process information
what are the folds in the cerebrum called?
gyri
how are gyri separated?
into areas by sulci and fissues
where is the thalamus found?
lies deep in brain tissue at the base of the cerebral hemisphere
what does the thalamus do?
relays info to and from cerebral cortex from sense organs
where is the hypothalamus found?
above pituitary gland
why is the hypothalamus important?
it links autonomic nervous and endocrine system
what is the optichiasma?
point where impulses from retinas cross over
where does the left cerebral hemisphere get information from?
- outer side of retina of left eye
- inner side of retina of right eye
what is the olfactory lobe?
- processes information regarding smells
what is the mid brain?
- connects fore and hind brain
- surrounds cerebral aquaduct which contains cerebral spine fluid
what does the cerebellum do?
- co ordinates muscular activity
- helps maintain posture and balacne
where is the cerebellum found?
in the hind brain
what does the medulla oblongata contain and do?
- contains origins of some cranial nerves
- controls basic functions such as respiration and cardiovascular
where is the medulla oblongata found?
in the hind brain
where is the pons found?
in the hindbrain between the mid brain and medulla oblongata
what does the pons do?
contains fibres which carry impulses within the brain
what happens if the brain is deprived of oxygen for 1min?
decreased activity
what happens if the brain is deprived of oxygen for 3min?
irreversible damage
what are the meninges?
they enclose and protect brain and spinal cord
what are the three layers of the meninges?
- dura mater (outermost, adheres to skull bones but not vertebrae)
- arachnoid mater (pressed against dura due to CSF pressure)
- pia mater (innermost, attached to actual brain and spinal cord)
what is cerebrospinal fluid?
- clear, colourless fluid
- formed in ventricles
- fills subarachnoid space and ventricles
where does the cerebrospinal fluid drain from?
- via veins in pia/arachnoid mater
where is cerebrospinal fluid secreted from?
- small arterioles and capillaries of pia/arachnoid mater
- choroid. plexus in the brain ventricles
what are the functions of cerebrospinal fluid?
- protection of brain and spinal cord against bone
- nutrition of brain and spinal tissue
- pressure maintainance
what are the 4 brain ventricles?
- 2 laterals
- 1 diencephalon
- 1 hindbrain
what are the function of the brain ventricles?
to help keep brain buoyant and cushioned
what is internal hydrocephallus?
foramina/apertures of ventricles obstructed
what is external hydrocephallus?
drainage of CSF obstructed
what is the peripheral nervous system made up of?
voluntary and involuntary (autonomic) branches
what are the voluntary branches of the PNS made up of?
12 pairs of cranial nerves and 38 pairs of spinal nerves
what are the involuntary branches of the PNS made up of?
sympathetic and parasympathetic nerves
what does the voluntary branches of the PNS control?
skeletal muscle movements
what does the involuntary branches of the PNS control?
smooth muscle, cardiac, and glands
how many cranial nerves are there?
12 pairs which are numbered rostrally to caudally
what is the vagus nerve?
- X
- atypical cranial nerve which is part of the parasympathetic nervous system and slows the heart
what does stimulation of the vagus nerve result in?
bradycardia
what nerve does injuries from intubation affect?
hypoglossal
what can damage to the hypoglossal nerve cause?
- dysphagia
- tongue deviation
what is a reflex arc?
nerve pathway from stimulation through spinal cord to effector site
what does dorsal root damage cause?
- lost sensation
- cannot feel stimulus
- no message sent
what does ventral root damage cause?
- sensation is felt and message transmitted
- no message sent to effector
- cannot initiate protective action
what is the sciatic nerve?
nerve found in caudal thigh that can cause temporary or permanent paralysis
what is the phrenic nerve?
controls diaphragm (contract/expand)
what is the autonomic nervous system?
- involuntary part of the PNS
what is the autonomic nervous system divided into?
- sympathetic (close to spinal cord)
- parasympathetic (in walls of affector organs)
what part of the autonomic nervous system is adrenalin and nor adrenalin associated with?
sympathetic
what part of the nervous system is acetyl choline associated with?
parasympathetic
what are some parts of a neuron?
- dendrite
- soma
- axon
- nodes of ranvier
- axon terminal
- schwann cell
- myelin sheath
- nucleus
what does a dendrite do?
receive impulses and carry then towards the cells body
what are the gaps between the schwann cells called which allow nutrients?
nodes of ranvier
what are some types of glial cells?
- astrocytes
- oligodendrocytes
- microglia
- ependymal
what is the synaptic cleft?
gap between 2 neurons
what are the 12 cranial nerves in order?
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
auditory
glossopharyngeal
vagus
spinal accessory
hypoglossal
what can sympathetic nerves be known as?
adrenergic nerves
what can parasympathetic nerves be known as?
cholinergic nerves
what nerves are associated with the fight or flight response?
sympathetic and parasympathetic