lec 1 - overview of the nervous system Flashcards
Afferent:
conducted inward (input)
think sensory to the CNS
Efferent:
conducted outward (output)
think motor away from CNS
Sensory:
afferent input into CNS (pain, temperature, touch, etc.)
Motor:
efferent output from CNS (motor innervation to muscle)
Somatic:
refers to skeletal muscle and/or body wall
think limbs
Autonomic/Visceral:
refers to viscera and body cavities
Ganglion:
collection/group of neuronal cell bodies in PNS
Nucleus:
collection/group of neuronal cell bodies in CNS
Central nervous system (CNS) is made up of
Brain
Spinal cord
(all the neurons that make up the spinal cord, brainstem, and brain)
Peripheral nervous system (PNS) is made up of
Cranial nerves (12 pairs)
Spinal nerves (31 pairs)
2 divisions: somatic and autonomic
> neurons/ nerves that leave or branch off the CNS
> dorsal/ ventral roots
spinal nerves
dorsal/ ventral rami
cranial nerves
peripheral ganglia
sympathetic trunk
Overview of the Nervous System
> neurons can have part of their structure in the CNS and another part of their structure in the PNS
> lower motor neurons have their cell bodies in the ventral horn of the spinal cord, while their axons leave the spinal cord via spinal nerves to go to muscles to innervate them
> pseudounipolar sensory neurons have their cell bodies in the dorsal root ganglion, yet their central process enter the CNS so that we can integrate the sensory information
Information Flow in the Nervous System
Sensory receptor -> sensory/afferent input -> integration in CNS -> motor/efferent output -> effector ->
response
Afferents & Efferents:
joints, skin, skeletal muscle -> somatosensory fibers -> CNS -> somatomotor fibers -> skeletal muscle
viscera, vessels -> viscerosensory fibers -> CNS -> visceromotor fibers -> glands, smooth muscle, cardiac muscle
4 Modalities
somatic sensory
visceral sensory
somatic motor
visceral motor
Somatic sensory:
pain, temperature, touch, pressure, stretch, proprioception
Fibers convey impulses from skin, joints, and skeletal muscles
Visceral sensory:
pain, temperature, touch, pressure, stretch, proprioception
Fibers convey impulses from viscera, blood vessels, and glands
ex) stretch of the stomach
Somatic motor:
skeletal muscles
Fibers provide somatic motor innervation to skeletal muscles
Visceral motor:
smooth and cardiac muscles
Fibers provide autonomic (sympathetic and parasympathetic) motor innervation to smooth and cardiac muscles in viscera, blood vessels, and glands
Planes of Section
Horizontal/Transverse/Axial
Coronal/Frontal
Sagittal
When a plane of section lies somewhere between these three principal planes, it is referred to as oblique
horizontal/transverse/axial plane
divides the body into superior and inferior portions
The horizontal plane is orthogonal to the superior-inferior axis
frontal/coronal plane
divides the body into anterior and posterior portions
The coronal plane is orthogonal to the anterior-posterior axis
This plane is perpendicular to the long axis of the person’s body
sagittal plane
divides the body into right and left halves
The sagittal plane is orthogonal to the left-right axis
Midsagittal means that the section is in the sagittal plane at the midline of the body
Parasagittal means that the section is in the sagittal plane but is not at the midline of the body
The PNS has 2 divisions:
Somatic nervous system (SNS)
Autonomic nervous system (ANS)
Somatic nervous system (SNS):
Target/effector: skeletal muscle
1 motor neuron pathway
Cell body in CNS
Autonomic nervous system (ANS):
Target/effector: smooth muscle, cardiac muscle, and glands
> Sympathetic division
Parasympathetic division
Enteric division
2 motor neuron pathway
Preganglionic (presynaptic) neuron = Cell body in CNS
Postganglionic (postsynaptic) neuron = Cell body in PNS
sympathetic division =
“fight or flight” division
causing “stress”
responses in the body
> increasing heart rate
dilating the pupils
stimulating sweat glands to produce sweat
parasympathetic division =
“rest and digest” division
responsible for restful responses and digestion
> decreasing heart rate
constricting the pupils
stimulating peristalsis
enteric division =
regulates the gut tube
In general, sympathetic and parasympathetic divisions of the autonomic nervous system target the same organs, but they typically have opposing actions/effects
Sympathetic innervation to heart increases heart rate = “Fight or flight” response
> more widespread - goes to skin
Parasympathetic innervation to heart decreases heart rate = “Rest and digest” response
Major CNS Regions
> Cerebrum
Cerebellum
Diencephalon
Brainstem
(Mesencephalon/ midbrain, Pons, Medulla oblongata)
Spinal cord
cerebrum =
controls higher order cognitive functions, including intellect, reasoning, learning and memory, planning, and emotion
memory storage and processing
conscious and subconscious regulation of skeletal muscle contractions
cerebellum =
inferior to the cerebrum and posterior to the brainstem
has a right and left cerebellar hemisphere
Involved in balance and coordination
coordinates complex somatic motor patterns
adjusts output of other somatic motor centers in brain and spinal cord
diencephalon =
thalamus = relay and processing centers for sensory and motor information
hypothalamus = centers controlling emotions, autonomic functions, and hormone production
brainstem =
connects the diencephalon and spinal cord and controls daily functions that keep you alive: breathing and heartbeat centers
small part of the brain, but it is the only part that is required for life
many vital functions, including autonomic and homeostatic functions
brainstem 3 major components (from rostral to caudal):
Midbrain: maintains consciousness, alertness, and attention
Pons: input to cerebellum for coordination
Medulla (oblongata): cardiac and respiratory centers
mesencephalon =
processing of visual and auditory data
generation of reflexive somatic motor responses
maintenance of consciousness
pons =
relays sensory information to cerebellum and thalamus
subconscious somatic and visceral motor centers
medulla oblongata =
relays sensory information to thalamus and to other portions of the brain stem
autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities)
The __ is the largest part of the brain and is divided into right and left hemispheres by the longitudinal fissure
cerebrum
> receives sensory input from the contralateral side of the body and sends motor output to the contralateral side of the body
> The cerebrum controls the opposite side of the body = right cerebral hemisphere controls the left half of the body, and the left cerebral controls the right half of the body
Lobes of the Cerebrum
frontal
parietal
temporal
occipital
Frontal lobe:
motor control, speech, emotions, cognition, and executive functions
> intellect reasoning, decision making & reward
Parietal lobe:
detecting and interpreting sensations from the body (somatosensation)
> main sensory lobe
taste, speech, reasoning
Temporal lobe:
hearing, smell, emotions, and memory
> olfactory, auditory cortex
Occipital lobe:
detecting and interpreting visual information
> vision
insular lobe/cortex =
deeper cortical region that is located in the Sylvian/lateral fissure between the frontal and parietal and temporal lobes
involved in linking sensory experience and emotional reactivity
Cerebral Cortex
The cerebral cortex has gyri and sulci, which allows it to increase surface area without taking up more space
In neurodegenerative diseases, like Alzheimer’s disease, neurons in the cerebral cortex die:
> making the gyri smaller
sulci to increase in size
sulci fill with more CSF
older person falls, their brain will move more within their skull and is more susceptible to a concussion or contusion as the brain hits the skull
Gyrus:
elevated ridge on the cerebral cortex
Sulcus:
shallow depression/groove between gyri
Fissure:
deep depression/groove (typically between lobes of the cerebrum)
Gray-White-Gray Organization of Cerebrum
The outer gray matter of the cerebrum forms the cerebral cortex
White matter connects the cerebral cortex and deeper nucleic groups
The deep/internal gray matter of the cerebrum forms nuclei, basal ganglia, and parts of the limbic system
subcortical white matter = composed of myelinated axons that connect the cortex to deeper CNS regions
Corpus Callosum
largest commissural fiber bundle in the cerebrum
connects the right and left cerebral hemispheres
The corpus callosum is white matter
Layer III pyramidal neuron axons form the corpus callosum and connect the right and left cerebral hemispheres
located deep to the lobes of the cerebrum and most of it is superior to the lateral ventricles
Internal Capsule
contains sensory and motor axons of ascending and descending tracts and limbic system fibers
contains output fibers from the cerebral cortex and input fibers from the thalamus to the cerebral cortex
is the white matter that is located between the thalamus and the nuclei that form the basal ganglia (e.g., globus pallidus, caudate nucleus, putamen)
anterior limb of the internal capsule:
posterior limb of the internal capsule:
anterior = conveys limbic information to the prefrontal cortex
posterior = contains sensory and motor fibers
___ form the posterior limb of the internal capsule and then enter the cerebral peduncles (crus cerebri)
cortical efferent fibers (e.g., corticospinal tracts)
Primary Motor Cortex
Location (functional area): the primary motor cortex is in the precentral gyrus of the frontal lobe
Functions: execution of motor plans and voluntary movements
Contains upper motor neurons that control contralateral body movements
Somatotopic map = motor homunculus
The precentral gyrus is on ____
the lateral surface of the frontal lobe and continues medially
The primary motor cortex is in the ___
precentral gyrus
Primary Somatosensory Cortex
Location (functional area): the primary somatosensory cortex is in the postcentral gyrus of the parietal lobe
Functions: detects somatosensory information (e.g., touch)
> somatosensations (e.g., touch, pressure, vibration, proprioception, pain, and temperature
Receives sensory information from the contralateral side of the body
Somatotopic map = somatosensory homunculus
The primary somatosensory cortex is in the ___
postcentral gyrus
= posterior to the central sulcus
> receives sensory input from the thalamus via thalamocortical fibers that project to layer IV
Sensory and Motor Homunculi
Somatotopic organization: specific parts of body map to specific parts of CNS
upper motor neurous in primary cortex - specific arrangement - certain areas bigger/smaller depending on #, lots in face and hands
The diencephalon is a collection of nuclei deep in the cerebrum that links the __ and ___
cerebrum
brainstem
Diencephalon Major components:
Thalamus: key relay center for cerebrum
(every sensation except smell goes here first)
Hypothalamus: regulate homeostasis
Subthalamus: motor control
Epithalamus and pineal gland: regulate circadian rhythms
(receives info. about light/dark, secretes melatonin)
Pituitary gland: hormone regulation
Spinal Cord spinal levels
Cervical: 8 spinal levels
Thoracic: 12 spinal levels
Lumbar: 5 spinal levels
Sacral: 5 spinal levels
Coccygeal: 1 spinal level
