nervous system Flashcards
central nervous system components
brain and spinal cord
Peripheral nervous system components
- cranial nerves and branches
- spinal nerves and branches
- ganglia
- sensory receptors
Neuron structure
Dendrites - receive input from other neurons
Cell body - cellular functions
Axons - carries electrical signals to terminals + release neurotransmitters
Sensory neuron functions
detect changes in the external and internal environment
Motor neuron functions
controlling muscles or glands
Interneuron function
processing of information from CNS into motor neurons
4 main types of neuroglia in CNS
- astrocytes
- oligodenrocyte
- microglial
- ependymac
astrocytes - CNS
help maintain the appropriate chemical environment
oligodendrocytes - cns
produce the myelin sheath that surrounds axons - action potential.
microglia - CNS
act as immune cells in the CNS, destroying foreign organisms and damaged nervous tissue.
ependymal cells- CNS
responsible for the production of cerebrospinal fluid.
Schwann cells - PNS
produce a myelin sheath that wraps around axons of PNS neurons
Satellite cells - PNS
provide structural support and aid in the exchange of nutrients between neurons and the interstitial fluid
Myelinated vs unmyelinated
myelinated - fast conduction velocity
unmyelinated - slow conduction velocity
sodium-potassium pump
3 Na+ and 2 K+ = to achieve resting membrane potential.
Potassium leak channel
allows potassium to move down its concentration gradient and out of the cell
How is resting membrane potential established?
- K+ wants to move down the concentration gradient out of cells through K+ leak channels.
- Leave the inside more negative
- Eventually, the negative charge inside become so great, it resists the movement of K+ out of the cell. Negative attracts positive.
Graded potentials
a small deviation from the resting membrane potential of the neuron. Can make the cell more negative - hyperpolarizing and depolarising more positive.
summation
process in which graded potentials occurring close enough in time to each other can add together to produce a bigger change in the membrane potential
Voltage-gated channels
proteins that respond to changes in membrane potential by opening a channel in the membrane. Allows ions to move down their concentration gradient.
Action potential threshold
where voltage-gated sodium channels open.
An influx of Na+ onto the cell through these channels = action potential.
Role of CNS
- detects changes in the outside and inside environment
- controls the body’s responses to external and internal changes
- gernates emotions, memories, plans
Cranial meninges
surrounds and protects the brain
spinal meninges
surround and protects the spinal cord.
meninges layers
- dura mater
- Arachnoid mater
- Pia mater
Dura mater
most superficial and strongest layer
- composed of dense irregular connective tissue
- adheres to the interior surface of cranial bones
Arachnoid mater
- below dura mater
- an avascular covering (no blood)
- Between the two layers lies space with interstitial fluid
Pia mater
innermost membrane
- adheres to the surface of the brain and spinal cord
- between the arachnoid mater and the pia mater is the subarachnoid - filled with cerebrospinal fluid
Blood-brain barrier
- tight cell junctions between the endothelial cells of capillaries supplying the brain
- prevents the flow of many substances from the bloodstream into the interstitial fluid in the CNS
Cerebrospinal fluid + functions
the fluid that circulates through cavities in the brain/spinal cord.
- Mechanical protection = serves as shock-absorbing medium that protects the brain/spinal cord from hitting the walls of cranial cavity and vertebral canal.
- Chemical protection = provides the optimal chemical environment for neuronal function
- Circulation = provides a medium for the exchange of nutrients and wastes between the blood and the nervous tissue of the brain/spinal cord.
choroid plexuses
- where csf is formed
- network of capillaries in the walls of the ventricles
- filter the blood plasma and secrete the newly formed cerebrospinal fluid into the ventricles.
cerebral cortex
- region of grey matter that forms the outer portion of the cerebrum
- responsible for most of our ‘higher-level’ brain functions