Nervous System Flashcards
complex network of neurons and supporting structures that regulates and coordinates body activities
nervous system
three main parts of the nervous system
- brain
- spinal cord
- nerves
functions of the nervous system
- communication and coordination
- control muscles and movement
- sensory perception
- regulation of internal organs
- learning, memory, and thought
- response to stimuli
two parts of the nervous system
- central nervous system
- peripheral nervous system
composed of the brain and spinal cord
central nervous system
composed of all the nerves outside the CNS, including cranial and spinal nerves
peripheral nervous system
two types of cells in the nervous system
- neurons
- glial cells
transmit electrical signals
neurons
three overlapping functions of the nervous system that work together to enable skilled movement
- sensory output (sensory)
- integration output
- response (motor output)
Three parts of the neuron
- cell body
- dendrites
- axon
central part of a neuron that contains the nucleus and controls the cell’s functions
cell body
afferent component of a neuron
dendrites
sends signals away
axon
parts of the axon
- axon hillock
- myelin sheaths
area where axon leaves the neuron cell body
axon hillock
highly specialized insulating layer of cells
myelin sheaths
Different kinds of neurons
- unipolar neurons
- bipolar neurons
- pseudounipolar neurons
- multipolar neurons
- have only one structure extending from the soma
- only occur in invertebrates
unipolar neurons
- have one axon and one dendrite extending from the soma
bipolar neurons
contain one axon and many dendrites
multipolar neurons
have a single structure that extends from the soma, which later branches into two distinct structures.
pseudounipolar neurons
Types of neurons
- sensory neurons
- motor neurons
- interneurons
- aka afferent neuron
- carry nerve impulses from sensory receptors in tissues and organs to the CNS
sensory neurons
- aka efferent neurons
- carry nerve impulses from the CNS to the muscles and glands
motor neurons
carry nerve impulses back and forth often between sensory and motor neurons within the spinal cord or brain
interneurons
where are interneurons found
exclusively in the CNS (brain and spinal cord)
are the supportive cells of CNS and PNS both physically and metabolically
glial cells
Different types of glial cells
- Schwann cells
- oligodendrocytes
- microglial cells
- ependymal cells
- astrocyte
- type of glial cell that surrounds neurons, keeping them alive and sometimes covering them with a myelin sheath
- major glial cell type in the peripheral nervous system
Schwann cells (SCs)
responsible for producing and maintaining the myelin sheath of the central nervous system
Oligodendrocytes
- acts as immunce cells of the CNS
- help protect the brain by removing bacteria and cell debris
- resident cells of the brain that regulate brain development, maintenance of neuronal networks, and injury repair
microglia
what does the microglia regulate
- brain development
- maintenance of neuronal networks
- injury repair
form an epithelial layer that lines the ventricles and central canal of the brain and spinal cord, respectively
ependymal cells
- help form the blood-brain barrier
- also involved in material exchange
- make up the majority of cells in the human central nervous system (CNS)
- can inhibit and stimulate te signaling activity of nearby neurons
astrocytes
what is membrane potential
localized electrical gradient across membrane
- non-excited state
- usually -70mV
resting membrane potential
3 sodium ions out, 2 potassium ions in
sodium-potassium pump
sudden, fast, transitory, and propagating change of the resting membrane potential
action potential
different parts of the action potential
- hypopolarization
- depolarization
- overshoot
- repolarization
- hyperpolarization
initial increase of the membrane potential to the value of the threshold potential
hypopolarization
threshold potential opens voltage-gated sodium channels, causing large influx of sodium ions
depolarization
phase during an action potential when the inside of a neuron becomes positively charged relative to the outside
overshoot
restore the resting membrane potential
repolarization
membrane potential is more negative than the default membrane potential
hyperpolarization
two types of synaptic tranmission
- electrical synapse
- chemical synapse
- less common but faster
- allow direct electrical communication between neurons via gap junctions
electrical synapses
- most common type
- neurotransmitters are released from the presynaptic neuron into the synaptic cleft
chemical synapses
Key features of electrical synapses
- gap junctions
- bidirectional signal transmission
- speed
- synchronization of neurons
electrical synapse occur at these structures
gap junctions
electrical signals can pass in both directions between the connected neurons
bidirectional signal transmission
because there is no need for neurotransmitter release and binding, communicated across electrical synapses is extremely fast almost instantaneous
speed
speed of electrical synapse
extremely fast
electrical synapses are important for synchronizing the activity of groups of neurons
synchronization of neurons
Key Steps in Chemical Synapses
- action potential reaches the presynaptic terminal
- calcium influx
- neurotransmitter release
- postsynaptic response
postsynaptic response can lead to what?
- depolarization
- hyperpolarization
if excitatory neurotransmitters are involved, the postsynaptic membrane becomes less negative, moving closer to the threshold for firing an action potential
depolarization
if inhibitory neurotransmitters are involved, the membrane becomes more negative, moving farther from the threshold, making it less likely to fire an action potential
hyperpolarization
two types of chemical synapses
- excitatory synapses
- inhibitory synapses
type of neurotransmitter that causes depolarization
excitatory neurotransmitters
type of neurotransmitter that causes hyperpolarization
inhibitory neurotransmitters
Example of neurotransmitters
- acetylcholine
- dopamine
- glutamate
- gamma-aminobutyric acid (GABA)
role of acetylcholine
excitatory neurotransmitter at neuromuscular junctions
role of dopamine
modulates reward, motor control
role of glutamate
main excitatory neurotransmitter in the CNS
role of gamma-aminobutyric acid (GABA)
main inhibitory neurotransmitter in the CNS
Two primary processes of signal integration
- temporal summation
- spatial summation
occurs when multiple signals arrive at a single synapse in rapid succession
temporal summation
- emerges from multiple presynaptic neurons
- occurs when stimuli are applied at the same time, but in different areas, with a cumulative effect upon membrane potential
- uses multiple synapses acting simultaneously
spatial summation
Main parts of the brain
- cerebrum
- cerebellum
- brainstem
- outer layer of the brain
- associated with higher brain functions like cognition, sensory perception, voluntary movement, and language
cerebral cortex
brain functions of the cerebral cortex
- cognition
- sensory perception
- voluntary movement
- language
Four lobes of the cerebral cortex
- frontal lobe
- parietal lobe
- temporal lobe
- occipital lobe
responsible for reasoning, planning, problem-solving, and voluntary movements
frontal lobe
processes sensory information such as touch, temperature, and pain
parietal lobe
involved in processing auditory information and memory
temporal lobe
responsible for visual processing
occipital lobe
- located at the base of the brain and connects to the spinal cord
- responsible for essential life-sustaining functions
- serves as a relay center for transmitting information between the brain and the rest of the body
brainstem
functions of the brainstem
- breathing
- heart rate
- sleep cycles
- coordination of reflexes
- located at the back of the brain under the cerebral cortex
- plays a critical role in motor control
- helps coordinate voluntary movements such as posture, balance, and coordination
- ensures that movements are smooth and precise
cerebellum
functions of the cerebellum
voluntary movements:
1. posture
2. balance
3. coordination
- major pathway for transmitting information between the brain and the body
- extends from the brainstem down the length of the spine and is protected by the vertebral column
spinal cord
Two primary functions of the spinal cord
- reflex actions
- transmission of sensory and motor information
automatic, involuntary responses to stimuli
reflex actions
pathway for reflex actions
reflex arc
parts of the reflex arc
- sensory neurons - detect stimulus
- interneurons - process information
- motor neurons - activate muscle response
- sensory information from the body travels up the spinal cord to the brain
- includes signals about touch, pain, temperature, and body position
sensory pathway
- motor commands from the brain travel down the spinal cord to the muscles
- these pathways control voluntary movments like walking, lifting, and speaking
motor pathways
- parts of the nervous system that lies outside the brain and spinal cord
- plays a key role in both sensory (afferent) input and motor (efferent) output pathways
- has 43 different segments of nerves
- subdivided to somatic NS and autonomic NS
- responsible for reflex arc
peripheral nervous system
peripheral nervous system plays a key role in both what?
- sensory (afferent) input
- motor (efferent) output
pathways
how many segments does the peripheral nervous system have
43 diferent segments
division of the 43 different segments of the PNS
- 12 pairs of cranial nerves
- 31 pairs of spinal nerves
Subdivision of the PNS
- somatic NS
- autonomic NS
- carry information in and out of the brain
- each has different function for sense or movement
- 10 originated from brainstem and mainly control voluntary movement and structures of the head
- 2 of them, olfactory and optic nerve nuclei, are not considered true because they are located in the forebrain and thalamus
cranial nerves
how many cranial nerves originated from brainstem
10
not considered as true cranial nerves
- olfactory nerve nuclei
- optic nerve nuclei
why are the olfactory and optic nerve nuclei not considered as true cranial nerves
because they are located in the forebrain and thalamus
mnemonics for cranial nerves
- oh
- oh
- oh
- to
- touch
- and
- feel
- very
- giant
- volcano
- ahh
- hot
what are the cranial nerves
- olfactory
- optic
- oculomotor
- trochlear
- trigeminal
- abducens
- facial
- vestibulocochlear
- glossopharyngeal
- vagus
- accessory
- hypoglossal
sensory only cranial nerves
- olfactory
- optic
- vestibulocochlear
motor cranial nerves
- oculomotor
- trochlear
- abducens
- accessory
- hypoglossal
both sensory and motor nerves
- trigeminal
- facial
- glossopharyngeal
- vagus
smell
- olfactory
vision
- optic
serves muscles of the eye
- oculomotor
serves the superior oblique eye muscles
- trochlear
- sensory from face and mouth
- motor to muscles of mastication
- trigeminal
serves the lateral rectus eye muscle
- abducens
serves the muscles of facial expression, lacrimal glands, and salivary glands
- facial
equilibrium and hearing
- vestibulocochlear
serves the pharynx (throat) for swallowing, posterior 3rd of tongue, parotid salivary gland
- glossopharyngeal
sensation from visceral (internal) organs, and parasympathetic motor regulation of visceral organs
- vagus
serves muscles that move head, neck, and shoulders
- accessory
serves muscles of the tongue
- hypoglossal
- carry somatosensory information and motor instructions from the spinal cord
- help control the function and movement of the rest of the body
- 31 pairs
spinal nerves
what do spinal nerves carry
somatosensory information
how many pairs are there in spinal nerves
31 pairs
what are the 31 pairs of spinal nerves
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
- carry information from sensory receptors of the skin and other organs to the central nervous system
- involves the special senses of vision, hearing, smell, and taste, as well as the sense of touch, pain, and temperature
- associated with specialized sensory receptors according to the stimuli they respond to
afferent (sensory) neurons
Different kinds of receptors
- exteroceptors
- interceptors
- proprioceptors
near the external surface, keep an animal informed about its external environment
exteroceptors
internal parts of the body, receive stimuli from internal organs
interceptors
in muscles, tendons, joints, sensitive to changes in tension of muscles and provide an organism with a sense of body position
proprioceptors
form of energy to which the receptors respond
- chemical
- mechanical
- light
- thermal
- specialized sensory receptors designed for detecting environmental status and change
- first level of environmental perception; they are channels for bringing information to the central nervous system
sense organs
what do sensory receptors with a sense organ do
transform energy from stimulus into nerve action potentials
- carry motor information away from the central nervous system to the muscles and glands of the body
- specifically, they carry signals from the brain to the PNS in order to initiate action
efferent neurons
- associated with voluntary control of muscles via skeletal muscles
- responsible for all the functions we can consciously influence such as moving our legs, arms, and other body parts
- main function: connect the CNS with organs and striated muscles to perform daily functions
somatic nervous system
regulates involuntary body responses
autonomic division
voluntary movement by skeletal muscles
somatic division
- regulates involuntary physiological processes including heart rate, blood pressure, respiration, digestion and sexual arousal
- sympathetic vs. parasympathetic divisions
- physiological responses to stress and relaxation
autonomic nervous system
two divisions of the autonomic nervous system
- sympathetic
- parasympathetic
- network of nerves that helps your body activate its “fight-or-flight” response
- system’s activity increases when you’re stressed, in danger or physically active
sympathetic nervous system
- network of nerves that relaxes your body after periods of stress or danger
- also helps run life-sustaining processes, like digestion, during times when you feel safe and relaxed.
parasympathetic nervous system
- largest and most complex unit of the PNS
- sometimes called a second brain because it can independently control digestive activities
enteric nervous system
interneuron connects motor neurons on both sides of the spinal cord, such that stimulation of muscle fibers in more than one part of the body allows coordination of muscle responses to stimuli
multisynaptic reflex arc
- process that involves adaptive structural and functional changes to the brain
- the ability of the nervous system to change its activity in response to instrinsic or extrinsic stimuli by reorganizing its structure, functions, or connections
- this process of brain changes occur after injury which can be beneficial, neutral, or negative
neuroplasticity
what is neuroplasticity
ability of the brain to form and reorganize synaptic connections, especially in response to learning or experience or following injury.
how can neuroplasticity be beneficial
restoration of function after injury
how can neuroplasticity be negative
can have pathological consequences
Three phases of neuroplasticity
- first 48 hours
- following weeks
- weeks to months afterward
first 48 hours of neuroplasticity
cell death, brain attempts to use secondary neuronal networks
following weeks of neuroplasticity
- recruitment of support cells as cortical pathways shift from inhibitory to excitatory
- synaptic plasticity and new connections are made
week to months afterward of neuroplasticity
brain continues to remodel itself via axonal sprouting and further reorganization around damage
- network of vessels that clear waste from the CNS, mostly during sleep
- promote efficient elimination of soluble proteins and metabolites from the CNS
glympathic nervous system
Common Disorders of the Nervous System
- epilepsy
- Alzheimer’s disease
- anosmia
- CIPA (congenital insensitivity to pain with anhidrosis)
- colorblindness
- spinal cord injury
- long-term chronic disease that causes repeated seizures due to abnormal electrical signals produced by damaged brain cells
- recurrent seizures
epilepsy
changes in awareness, muscle contrl, sensations, emotions, and behavior
seizures
what does epilepsy disrupt
rhythmic electrical impulses, causing bursts of uncontrolled electrical energy
- progressive decline in memory, thinking, learning, and organizing skills
- most common in people over 65
Alzheimer’s Disease
general term for symptoms like memory loss and difficulty thinking
dementia
misprocessed beta-amyloid proteins clump together, disrupting communication between brain cells
amyloid plaques
twisted tau proteins collpase cellular transport tracks, leading to cell dysfunction and death
tau tangles
- inability to detect odors
- often leads to diminishes taste
- can still recognize basic tastes (sweet, sour, salty, bitter, umami)
anosmia
- rare genetic disorder leading to inability to fell pain and reduced sweating
- susceptible to serve injuries without awareness
CIPA (congenital insensitivity to pain with anhidrosis)
difficulty sweating, affecting body temperature regulation
anhidrosis
- cause malfunctioning TrkA protein, crucial for sensory neuron survival
- leads to self-destruction of pain-sensing neurons
NTRK1 Gene mutations
caused by the absence or malfunction of cones in the retina, which are responsible for color vision
colorblindness
process light and images, sending signals to the brain for color perception
cones
types of cones
- red-sensing cones (L cones)
- green-sensing cones (M cones)
- blue-sensing cones (S cones)
- L cones
- sensitive to long wavelength
- around 560 nm
red-sensing cones (L cones)
- M cones
- sensitive to medium wavelengths
- around 530 nm
green-sensing cones (M cones)
- S cones
- sensitive to short wavelenghts
- around 420 nm
blue-sensing cones (S cones)
most common type of colorblindness
red-green color blindness
different types of red-green color blindness
- protanopia
- deuteranopia
- protanomaly
- deuteranomaly
- L cones missing
- colors appear as shades of blue/gold
- unable to perceive red light
protanopia
- M cones missing
- sees mainly blues and golds
- unable to perceive green light
deuteranopia
- L cones less sensitive
- red light appears darker
protanomaly
- M cones less sensitive
- greens appear muted
deuteranomaly
types of blue-yellow colorblindess
- tritanopia
- tritanomaly
- S cones missing
- colors appear mainly red, light blue, pink, and lavender
tritanopia
- S cones are less sensitive
- blues look green, and yellow perception is diminished
tritanomaly
rarest form of colorblindness
monochromacy
Types of monochromacy
- blue cone monochromacy
- rod monochromacy (achromatopsia)
- only S cones are functional
- see mostly in shades of grey
blue cone monochromacy
- no functional cones
- vision in shades of gray
rod monochromacy (achromatopsia)
- supports the skull or the weight of the head
- protects upper portion of the spinal cord
cervical spine (C1-C7)
specially designed for head rotation and support
- C1 (atlas)
- C2 (axis)
potential effects of cervical spine injury
- quadriplegia
- breathing problems
loss of function/sensation in all four limbs
quadriplegia
higher cervical injuries can affect diaphragm function
breathing problems
- provides stability and support to the rib cage, which protects vital organs such as the heart and lungs
- allows limited movement compared to cervical and lumbar due to connection to ribcage
thoracic spine (T1-T12)
supports upper body weight, facilitates body movement, and controls leg functions
lumbar spine (L1-L5)
provides sensation to the groin and genital aria, helps move hip musles
L1 spinal nerve
provide sensation to the front of the thigh and inner lower leg, control hip and knee movements
L2 - L4 spinal nerves
sensation to the outer lower leg and upper foot, contrls hip, knee, foot, and toe movements
L5 spinal nerve
formed by L4, L5, and sacral nerves, runs from the pelvis down the back of the leg to the foot
sciatic nerve
- part of the peripheral nervous system
- involved in sensory and motor control in the pelvic area, legs, bladder, and sexual functions
sacrum (S1-S5)
- controls plantar flexion (pointing toes) and knee/hip movements
- provides sensation to the outer leg and foot
S1 nerve
- assists with hip and knee movemnts
- controls pelvic floor muscles
- provides sensation to the back of the thigh and knee
S2 nerve
- similar to S2 nerve
- involved in thigh sensation and movement
S3 nerve
controls pelvic floor muscles, especially bowel movement control
S4 nerve
a network of nerves (S1-S4) controlling hip movements, leg sensation, and includes the sciatic nerve
sacral plexus
effect of sacrum injury
- loss of bladder/bowel control
- sexual dysfunction
- leg weakness
- tailbone, 3-5 fused vertebrate
- bottom of the spine, providing attachment to points for muscles, tendons, and ligaments related to sitting and pelvic floor support
- supports body weight when seated and helps balance
coccyx
how many fused vertebrate are there in the coccyx
3-5
