Nervous System Flashcards
What are the 2 divisions of the nervous system?
- Central Nervous System (brain & spinal cord)
- Peripheral Nervous System (cranial & spinal nerves, and ganglia)
What is the function of the CNS?
- integration and processing of info
- coordinate sensory input & motor output
What is the function of the PNS?
- transmit sensory info to CNS (afferent)
- carry impulse to muscles glands (efferent)
Compare afferent & efferent
afferent = info received & sent to CNS (arrives at CNS)
efferent = CNS send interpretation of info to muscles/glands (exits CNS)
Describe the tree of the PNS
- Sensory (afferent division)
a. somatic sensory
b. visceral sensory - Motor (efferent division)
a. somatic motor
b. automatic motor
i. sympathetic
ii. parasympathetic
Somatic sensory
sensory receptors in skin, fascia, joints, skeletal muscles, special senses (in sensory afferent division
Visceral sensory
sensory receptors in viscera (smooth/cardiac muscle & organs) (in sensory afferent)
Somatic Motor
“voluntary” nervous system: innervates skeletal muscle (motor efferent)
Automatic motor
“involuntary” nervous system: innervates cardiac & smooth muscle (motor efferent)
What are the two cell types within neural tissue?
- neurons
- neuroglia
Neurons
make up nerves - approximately 20 billion in human body - most cannot divide
Bundles of cell bodies & axons in CNS
bundle of cell bodies = nuclei
bundle of axons = tract
Bundles of cell bodies & axons in PNS
bundle of cell bodies = ganglion
bundle of axons = nerve
Neuroglia (5):
- supportive framework for neuron
- approx 100 billion glial cells
- small and mitotically active
- regulate extracellular environment
- nervous system is 50:50 mixture of neurons & glial cells
What are the types of glial cells in the CNS (4)
- astrocytes
- oligodendrocytes
- microglia
- ependymal cells
What are the types of glial cells in PNS (2)
- satellite cells
- Schwann cells
Astrocytes (4) functions:
Largest, most abundant glial cells
1. regulate ion composition of ECF
2. help maintain blood-brain barrier
3. repair damaged neural tissue
4. structural framework for neurons
What cell junctions are in blood-brain barrier?
tight junctions
Oligodendrocytes (4)
- fewer processes than astrocytes
- processes connect a few axons
- wrap axons in sheath of myelin
- CNS version of Schwann cells
What creates the white matter of the brain and how does this differ from brain gray matter?
The white matter of the brain is created by the myelin of oligodendrocytes and the grey matter lacks myelin
White vs gray matter
gray - somas & unmyelinated axons
white - myelinated axons
Microglia
- smallest glial cell
- remove waste & pathogens by phagocytosis
Ependymal cells
- line ventricles & central canal
- monitor composition of CSF
Satellite cells
- surround cell bodies of ganglia
- regulate waste nutrient diffusion between ECF and cell bodies
2 Steps to formation of myelin sheath
- Schwann cells wrap around axon several times
- nucleus pushed to periphery
What part of the Schwann cell is the myelin sheath?
Schwann cell plasma membrane
Myelinated vs unmyelinated
myelinated - has multiple layers of Schwann cell membrane
unmyelinated - single layer of Schwann cell plasma membrane
What are the 2 functional classes of neurons?
- sensory neurons - afferent
- motor neurons - efferent
Functions of interneurons (3)
- perform intergration
- receive, process, and store information
- “decide” proper response to stimulus
Anatomical classes of neurons (4)
- anaxomic
- bipolar
- pseudounipolar/unipolar
- multipolar
Anaxomic (4)
- lacking axons
- cannot distinguish dendrites from axons
- rare
- found in retina
Bipolar (3)
- two ends
- 2 poles coming off soma
- in retina
Pseudounipolar
- cell body off to the side
- one pole exits soma
- dendrite straight to axon - don’t go through soma
- in sensory neurons of PNS
Multipolar (3)
- many poles from soma
- most common neuron
- found in motor and interneurons
What type of innervation circuit?
diverging: single input - multiple outputs
What type of innervation circuit?
converging: multiple inputs - single output
What kind of cells allow convergence in the cerebellum?
Purkinje cells (highly branched dendrites, receive stimuli from 1000s of neurons)
6 Regions of Human Brain:
- Cerebrum
- Cerebellum
- Medulla Oblongata
- Pons
- Mesencephalon (mid-brain)
- Diencephalon (pineal, thalamus)
What is the outer gray matter in cerebrum?
telencephalon
What are the lobes of the cerebrum?
- frontal
- temporal
- occipital
- parietal
- insular
Central sulcus function
separates frontal & parietal lobes
Frontal lobe components (2)
- primary motor cortex (precentral gyrus)
- prefrontal cortex (frontal association area)
Primary motor cortex - location & function (2)
aka (precentral gyrus) of frontal lobe
1. skeletal muscle control
2. directs somatic motor neurons (voluntary)
Prefrontal cortex - location & function (4)
aka frontal association area of frontal lobe
- reasoning skills
- predicting future events & consequences
- temporal relationship between events
- motivation
Parietal lobe
has post-central gyrus = primary somatosensory cortex
Primary somatosensory cortex: location, function
post-central gyrus of parietal lobe
process sensation of touch, pain, taste, temperature
Why is the touch on your arm different from your hand?
more convergence in arm - think of homunculus man (smaller area increase convergence and vice versa)
What is the contralateral nature of motor & sensory cortices?
control right arm movement with left motor cortex and same for sensory - opposites
What are the 3 association areas of the cortex and their functions:
- somatic sensory association area - interpret size, shape, and texture (feel keys in pocket)
- visual association area - visual interpretation
- auditory association area - sound interpretation
Temporal lobe 4 special regions
- olfactory cortex
- auditory cortex
- hippocampus
- amygdala
Hippocampus
short-and-long term memory formation (a nucleus deep in temporal lobe)
Amygdala
- processing of emotions
- size correlates positively with aggression
How does the amygdala differ in those with normal activity and those with PTSD?
normal: emotional learning & self-reflection
PTSD: “survival mode” - hypervigilant
Occiptial lobe function
- visual cortex - stimuli arrive
- visual association arrive - visual interpretation
Insular lobe
gustatory cortex (behind temporal & frontal lobe)
How do we know the somatosensory regions?
- historically via epileptic surgery
- fMRI - O2-rich blood indicates brain activity - (Linus Pauling…. proposed DNA triple helix, discovered α-helix & β-pleated sheet, and difference in magnetic pull of O2 rich & O2 poor blood)
Cerebellum Functions (3)
- balance
- coordination of body movements
- proprioception (awareness of body in space)
Medulla Oblongata Functions (3)
- connects spinal cord to brain
- relay station for sensory and motor stimuli
- autonomic nervous system control centers (cardiovascular, vasomotor, respiratory)
Cardiovascular control center functions (2)
- regulate heart rate
- regulate strength of contraction
(found in medulla oblongata)
Vasomotor control center function
distribution of blood flow (found in medulla oblongata)
Respiratory control center
rhythmicity of breathing (found in medulla oblongata)
Pons Functions
- sleep/wake cycles
- switch from inspiration to exhalation
Mesencephalon structures
aka “Mid-brain”
1. corpora quadrigemina
2. cerebral aqueduct
Superior colliculus functions
part of corpora quadrigemina
1. integrates visual information with other senses
2. visually track moving objects
3. initiate reflex to visual stimulus
Inferior colliculus functions
part of corpora quadrigemina
1. relay auditory information to thalams
2. startle response to auditory stimuli
Cerebral Aqueduct function
sends cerebral spinal fluid where it is needed
Diencephalon structures
- pineal gland
- thalamus
- hypothalamus
Pineal gland functions
- secretes melatonin
- controls sleep/wake cycle
- secretion varies by age (teen sleep cycle)
Where is the pineal gland in lizards and what is its function?
It is on the top of their head - it is called pineal eye - light triggers afferent impulse to pineal gland
Thalamus function
“switchboard” for sensory & motor information to and from cerebral cortex
Hypothalamus function
- controls drive for thirst, hunger, and sex
- helps regulate blood pressure, body temperature, and heart rate
- endocrine gland - releases hormones
Pituitary gland functions
major endocrine gland (growth hormone, luteinizing hormone, follicle-stimulating hormone, antidiuretic hormone (Vasopressin))
What are the 3 meningeal layers?
- dura mater
- arachnoid mater
- pia mater
Dura mater layers
- endosteal layer
- dural sinus
- meningeal layer
Arachnoid mater parts
- arachnoid membrane
- subarachnoid space
- arachnoid trabeculae (support vasculature)
Pia mater location
is bound to surface of brain by astrocytes
Functions of Cerebral Spinal Fluid
- pad neural tissue from bone
- supports the brain
- removal of wastes by glymphatic system
What area synthesizes CSF?
choroid plexus
How is CSF made (4)?
- CSF constantly produced at each choroid plexus
- most CSF enters subarachnoid space at 4th ventricle
- flows through CNS
- enters superior sagital sinus via arachnoid granulations/villi
- goes back into circulatory system and repeats
How can we control when we pee?
- prefrontal cortex sends inhibitory signal
- inhibition overridden during SEVERE stress
axosomatic synapse
synapses that are made onto the soma or cell body of a neuron
axodendritic synapse
synapse that one neuron makes onto the dendrite of another neuron - most common (axon to dendrite)
axoaxonic synapse
synapse from one axon to another
