Nervous System (week 4) Flashcards
what are the functions of the nervous system?
- sensory input
- integration
- major input
what is sensory input?
gathering information
- sensory receptors monitor changes, called stimuli, occurring inside and outside the body
what is integration?
where the nervous system processes and interprets sensory input and decides whether action is needed
what is motor input?
a response, or effect, activates muscle or glands
what are the two structural classification?
central nervous system and peripheral nervous system
what are the 2 functional classification?
sensory (afferent) division or motor (efferent) division
what are the two cell types in nervous tissue?
neurons and neuroglia (support cells in the CNS)
describe neuroglia cells
- resembles neurons
- unable to conduct nerve impulses
- never lose the ability to divide
what are the functions of neuroglia?
to support, insulate and protect neurons
what are the various PNS glial cells?
schwann and satellite cells
what are schwann cells?
form myelin sheath around nerve fibres in the PNS
what are satellite cells?
protect and cushion neuron cell bodies
what are the various CNS glial cells (support cells)?
astrocytes, microglia, ependymal cells and oligodendrocytes
what are astrocytes?
abundant, star-shaped cells
- brace and anchor neuron to blood capillaries
- protect neurons from harmful substances in blood
- control the chemical environment of the brain
- determine permeability and exchanges between blood capillaries and neurons
what are microglia
spider like phagocytes
- monitor health of nearby neurons
- dipole of debris
what are ependymal cells?
line cavities of the brain and spinal cord
* cilia assist with circulation of cerebrospinal fluid
what are oligodendrocytes?
wrap around nerve fibres in the central nervous system
- produce myelin sheaths
what is ganglia?
collections of cell bodies outside the CNS in the PNS
what are tracts?
bundles of nerve fibres in the CNS
what are nerves?
bundles of nerves fibres in the PNS
what are processes in the nervous tissue neurons?
fibres that extend from the cell body
what are sensory (afferent) neurons?
carry impulses from the sensory receptors to the CNS
what are the receptors included in sensory (afferent) neurons?
cutaneous sense organs (in skin detect pain, temperature, touch, pressure)
and proprioceptors in muscles and tendons detect stretch
what are motor (efferent) neurons?
carry impulses from the central nervous system to viscera and or muscles and glands
what are interneurons (association neurons)?
cell bodies located in the CNS
—> connect sensory and motor neurons
what are the functional properties of neurons?
irritability and conductivity
what is irritability in the functional properties of neurons?
ability to respond to a stimulus and convert it to a nerve impulse
what is conductivity in the functional properties of neurons?
ability to transmit the impulse to other neurons, muscles or glands
what is a unipolar neuron?
a neuron that has a short single procee leaving the cell body
- > sensory neurons found in the PNS ganglia
- > conduct impulses both toward and away from the cell body
what is a bipolar neuron?
one axon and one dendrite
-> located in special sense organs, such as nose and eye
what is a multipolar neuron?
many extensions from the cell body
- > all motor and interneurons are multipolar
- most common structural type
what are the electrical conditions of a resting neuron’s membrane?
- plasma membrane at rest is inactive (polarised)
- fewer positive ions are inside the neuron’s plasma membrane than outside
* K+ is the majorly positive ion inside the cell
* Na+ is the major positive ion outside the cell - the polarised membrane is more permeable to K+ than Na+
- as long as the inside of the membrane is more negative (fewer positive ions) than the outside, the cells remain inactive
what are the steps in the nerve impulse?
- resting membrane is polarised
- stimulus initiates local depolarisation
- depolarisation and generation of action potential
- propagation of the action potential
- repolarization
- initial ionic conditions restored
(nerve impulse) explain when the resting membrane is polarised
- external is slightly positive, extracellular ion is Na+
- internal is slightly negative, intracellular ion is K+
* more permeable to K+ ions
what happens when a stimulus changes the permeability of the neurons membrane to sodium ions?
sodium channels now open, and sodium (Na+) diffuses into the neuron
(inward rush of Na+) ions changes the polarity= depolarization
(the nerve impulse) explain where the stimulus initiates local depolarisation
there is a rush of sodium ions into the cell
-> changes polarity of the membrane
(inside more positive, outside more negative)
what is graded potential (local depolarization)?
where inside the membrane is more positive, the outside is less positive
(the nerve impulse) explain depolarization and generation of action potential
if stimulus is strong enough and sodium influx is great enough, local depolarization activates the neuron to conduct an action potential (nerve impulse)
(the nerve impulse) explain the propagation of the action potential
if enough sodium enters the cell, the action potential (nerve impulse) starts and is propagated over the entire axon
what kind of fibres conduct nerve impulse more quickly?
fibres with myelin sheaths
what is repolarization?
restoring inside membrane to negative charge, outer membrane to positive change
(the nerve impulse) explain repolarization
membrane permeability changes again
—> impermeable to sodium ions and permeable to potassium ions
- potassium ions rapidly diffuses out of the neuron, repolarization the membrane
how are the initial conditions of sodium and potassium ions restored?
using the sodium-potassium pumps- uses ATP to restore to original condition
(The nerve impulse) explain the where the initial ionic conditions are restored
the initial condition are restored using sodium-potassium pumps via the usage of ATP
-> 3 sodium ions eject, while 2 potassium ions are returned
*when the action potential reaches the axon terminal, the electrical charge opens calcium channels
what are the main brain regions?
cerebral hemispheres, diencephalon, brain stem and cerebellum
what are cerebral hemispheres ridges called?
gyri
what are cerebral hemisphere grooves called?
sulci
what are fissures?
deeper grooves
what are the 3 main regions of cerebral hemisphere?
- the cortex is superficial gray matter
- white matter
- basal nuclei are deep pockets of gray matter
what is the cerebral cortex known for?
primary somatic sensory area, primary motor area, broca’s area (motor speech area) and other specialised areas
where is the cerebral cortex located?
located in the parietal lobe, posterior to central sulus
what does the cerebral cortex do?
receive impulses from the body’s sensory receptors
—> pain, temperature, light touch (except for special senses)
what is sensory homunculus
a spatial map
what is basal nuclei?
islands of grey matter buried deep within the white matter of the cerebrum
what are the functions of basal nuclei?
regulate voluntary motor activities by modifying instructions sent to skeletal muscles by the primary motor cortex
where is the primary motor area located?
located anterior to the central sulcus in the frontal love
what does the primary motor area do?
allows us to consciously move skeletal muscles
what is motor hommuculus
a spatial map
what is broca’s area?
involved in our ability to speak
-> usually in left hemisphere at the base of the pre central gurus
what is diencephalon composed of?
thalamus, hypothalamus and epithalamus
where is the diencephalon located?
it sits on top of the brain stem, enclosed by the cerebral hemispheres
what is the function of the thalamus?
relays station for sensory impulses passing upward to the cerebral cortex
*encloses the third ventricle
what is the hypothalamus known for?
- important autonomic nervous system centre
- > regulates body temperature, water balance and metabolism
- houses the lambic centre for emotions
- regulates the nearby pituitary gland
- houses mammillary bodies (reflex centre for olfaction (smell)
what is the epithalamus known for?
- houses the pineal body (an endocrine gland)
- > includes the choroid plexus - forms cerebrospinal fluid
*forms the rood of the third ventricle
what are the 3 components of the brain stem?
- mid brain
- pons
- medulla oblongata
what is the function of the brain stem?
provides pathway for ascending and descending tracts
- produce programmed behaviours for key survival
describe the functions and area of the mid brain
- extends from the mammillary bodies to the pons inferiorly
- cerebral aqueduct (tiny canal) connects the third and fourth ventricles
- 2 bulging fiber tracts, cerebral penduncles, convey ascending and descending impulses
explain the functions and area of the pons
- the rounded structure protruding just below the mid brain
- mostly composed of fibre tracts
- includes nuclei involved in the control of breathing
explain the functions and area of the medulla oblongata
- the most inferior part of the brain stem that merges into the spinal cord
- includes important fibre tracts
- contains important centres that control:
- heart rate, blood pressure, breathing, swallowing and vomiting
- fourth ventricle lies posterior to pons and medulla
explain the area and functions of the reticular formation
- diffuse mass of gray matter along the brain stem
- involved in motor control of visceral organs
- reticular activating system (RAS)
—> plays a role in awake/sleep cycles and consciousness
—> filter for incoming sensory information
what is the cerebellum
2 hemispheres with convoluted surfaces
-> outer cortex of gray matter and inner region of white matter
what is the function of the cerebellum?
controls balance, provides precise timing for skeletal muscle activity and coordination of body movements
how is the central nervous system protected?
- bony protection (brain and spinal cord)
- meninges
- cerebrospinal fluid (CSF)
- blood-brain barrier
what are the layers of meninges?
Dura matter, arachnoid layer, pia matter, cerebrospinal fluid (CSF), blood-brain barrier
describe dura mater
- outermost leathery layer
- double-layered external covering
periosteal layer: attached to inner surface of the skull
Meningeal layer: outer covering of the brain - folds inward in several areas
-> falx cerebri
-> Tentorium cerebelli
describe the arachnoid layer
- middle later
- weblike extensions span the subarachnoid space to attach it to the pia matter
- subarachnoid space is filled with cerebrospinal fluid
- arachnoid granulation’s protrudes through the dura mater and absorb cerebrospinal fluid into venous blood
what is pia mater
- the internal layer
- clings to the surface of the brain and spinal cord
describe cerebrospinal fluid
- formed continually by the choroid plexuses
- CSF forms a watery cushion to protect the brain and spinal cord
- circulated in the arachnoid space, ventricles and central canal of the spinal cord
what are choroid plexuses?
capillaries in the ventricles of the brain
describe the blood-brain barrier
- includes the least permeable capillaries of the body
- allows water, glucose and amino acids to pass through the capillary walls
- excludes many potentially harmful substances from entering the brain, such as wastes
describe the spinal cord
it extends from the foremen magnum of the skull to the first or second lumbar vertebra
-> provides a 2 way conduction pathway to and from the brain
what is the spinal cord protected by?
vertebrae and meninges
how many pairs of spinal nerves arise from the spinal cord?
31 pairs
describe the gray matter of the spinal cord and spinal roots
- posterior (dorsal) horns house interneurons
- ventral (anterior) horns house motor neurons of the somatic (voluntary) nervous system
- gray matter surrounds the central canal, which is filled with cere-brospinal fluid
what are the functions of posterior (dorsal) horns?
they receive information from sensory neurons in the dorsal root; cell bodies housed in dorsal root ganglion
what are the functions of ventral (anterior) horns?
send motor information out the ventral root
what is white mater of spinal cord composed of?
myelinated fibre tracts
what are the 3 regions of white mater (spinal cord)
dorsal, lateral and ventral columns
what are the functions of sensory (afferent) tracts?
conduct impulses toward the brain
what are the functions of motor (efferent) tracts?
carry impulses from brain to skeletal muscles
what is the peripheral nervous system (PNS)?
a system that consists of nerves and ganglia (clusters of cell bodies) outside the CNS
what is the structure of a nerve?
- protective connective tissue coverings
- mixed nerves
- sensory (afferent) nerves
- motor (efferent) nerves
describe the protective connective tissue covering in detail
there is 3 layers, endoneumrium, perineurium and epineruium layers
what is endonerurium?
a connective tissue sheath that surrounds each fibre
what is perineurium?
a covering that wraps groups of fibres bound into a fasicle
what is epineurium?
a covering that binds groups of fascicles
what are mixed nerves composed of?
both sensory and motor fibres
what do sensory nerves do?
carry impulse towards the CNS
what do motor nerves do?
carry impulse away from the CNS
how mn]any pairs of nerves serve mostly the head and neck?
12 pairs
where does the only pair of vagus nerves extend to?
thoracic and abdominal cavities
how many spinal nerves are there?
31 pairs of spinal nerves
how are spinal nerves formed?
by the joining of the ventral and dorsal roots of the spinal cord
what is a plexus?
networks of nerves serving motor and sensory needs of the limbs
how many plexuses are there?
4
name each plexus
cervical, brachial, lumbar, and sacral
what is the autonomic nervous system
motor subdivision of the PNS
what are the functions of the autonomic nervous system
- controls the body automatically and is also known as the involuntary nervous system
- regulates cardiac and smooth muscles and glands
what are the 2 subdivisions of the autonomic nervous system?
somatic nervous system and autonomic nervous system
what is different about the somatic nervous system compared to the autonomic nervous system
- motor neuron cell bodies originate inside the CNS
- axons extends to skeletal muscles that are served
what is the difference of the autonomic nervous system compared to somatic nervous system?
- has a chain of two motor neurons
- preganglionic neuron is in the brain or spinal cord
- postganglionic neuron extends to the organ
- has 2 arms
- sympathetic division
- parasympathetic division
where does preganglionic neurons originate from?
- criminal nerves III, VII, IX, X
- S2 through S4 regions of the spinal cord
when body divisions serve the same organ they cause what effects?
they cause antagonistic effects due to different neurotransmitters
what do parasympathetic (cholinergic) fibres release ?
acetylcholine
what do sympathetic postganglionic (adrenergic) fibres release?
norepinephrine
what types of axons release both divisions release acetylcholine?
preganglionic axons
what are the 2 divisions in autonomic nervous system?
parasympathetic and sympathetic division
describe the sympathetic division
“fight or flight” division
- response to unusual stimulus when emotionally or physically stressed or threatened - “E” division * exercise, excitement, emergency, embarrassment
describe the parasympathetic division
“rest and digest” system
- conserves energy - maintains homeostasis, regulates digestion and elimination - “D” division * digestion * defecation * diuresis
