CNS, Mechanoreception and Nociception

more specific components of the central nervous system

1. cerebral hemispheres

2. diencephalon

3. cerebellum

4. brainstem

5. spinal cord

two main components of peripheral nervous system

sensory components and motor components

sensory components of the peripheral nervous system

1. sensory ganglia and nerves

2. sensory receptors 

main motor components of peripheral nervous system

1. visceral motor system

2. somatic motor system

visceral motor system components

1. sympathetic, parasympathetic, and enteric divisions

2. autonomic ganglia and nerves 

what does the visceral motor system act upon?

1. smooth muscles

2. cardiac muscles

3. glands

components of somatic motor system

motor nerves

what does the somatic motor system act upon?

skeletal (striated) muscles

gastrulation

1. when the blastula transforms into a multilayered gastrual with three germ layers

2. the hollow ball of cells folds in on itself

three germ layers of gastrula

1. endoderm

2. mesoderm

3. ectoderm

what does the endoderm become?

1. GI tract lining

2. glands that open to GI tract

3. lung

4. thyroid

5. urethra

what does the mesoderm become?

1. musculoskeletal system

2. dermis

3. connective tissue

4. heart

5. blood

6. spleen 

what does the ectoderm become?

1. CNS

2. cranial and sensory nerves

3. peripheral ganglia

4. pigment cells

5. hair

6. lens 

neurulation

formation of the neural tube from the ectoderm layer

types of cells in the neural tube 

1. neural precursor cells 

2. neuroblasts

3. neural crest cells

neural precursor cells

can self-renew and differentiate into different neurons and glial cells

neuroblasts

immature cells that act like neural stem cells, and can produce neurons and glial cells

neural crest cells

transient and migratory stem-cell-like cells that give rise to the PNS

functional unit of the nervous system

neurons

neurons

excitable cells that generate and carry electrical signals 

polarity of sensory neurons

1. pseudounipolar

2. bipolar

pseudounipolar neuron

sensory neuron with a single extension from its cell body that branches into two distinct axons (peripheral branch and central branch)

peripheral branch of pseudounipolar neuron

extends to sensory receptors of somatic sense

central branch of pseudounipolar neuron

travels into the CNS

bipolar neuron

have two distinct processes branching from the cell body: one axon and one dendrite

types of multipolar neurons

1. interneurons of CNS

2. efferent neurons

multipolar neuron definition

1. a neuron with multiple extensions from the cell body

2. can receive input from multiple locations

glial cells

1. no direct synaptic interactions of electrical signaling

2. provide supportive functions

3. found in the CNS and PNS

types of glial cells in the PNS

1. satellite cells

2. schwann cells 

satellite cells

support cell bodies

schwann cells

1. secrete neurotrophic factors that keep neurons alive

2. form myelin sheaths 

3. repairs the PNS from damage 

types of glial cells in the CNS

1. oligodendrocytes

2. astrocytes

3. microglia

4. ependymal cells 

oligodendrocytes

form myelin sheaths

astrocytes

1. form support for CNS

2. help form blood brain barrier

3. secretes neurotrophic factors

4. take up K+ and neurotransmitters 

microglia

1. modified immune cells that act as scavengers

2. macrophages of the CNS

3. secrete inflammatory signals 

ependymal cells

create barriers between compartments to prevent leaking

meninges

layers of connective tissue that sit under the cranium to protect the brain

meninges components

1. pia mater

2. arachnoid membrane

3. dura mater 

dura mater

outermost and thickest layer of meninges

subdural space 

space between the dura mater and arachnoid membrane

arachnoid membrane

web-like layer of connective tissue

subarachnoid space

space in between the webbed matrix of the arachnoid membrane 

pia mater

1. touches and covers the brain

2. not substantial physical protection

3. very thin 

total volume of CSF

125-150 mL

how often is CSF replaced?

3-4 times a day

how much CSF is produced in 24 hours?

500-600 mL

where is CSF found?

1. brain’s ventricles

2. subarachnoid space

3. central canal of spinal cord

what cells secrete CSF?

ependymal cells within the choroid plexus of the third ventricle

what is CSF made of?

mostly water with added solutes

main functions of CSF

1. adds buoyancy to the brain

2. waste removal from brain and spinal cord through exchange with interstitial fluid 

arachnoid villi

specialized structures on the arachnoid membrane that absorb some of the CSF back into the blood

meningitis

inflammation of the meninges that can be caused by bacteria, viruses, fungi, and parasites 

astrocyte foot processes

secrete paracrines that promote tight junction formation in capillaries in the brain

blood brain barrier

highly selective semipermeable border of endothelial cells that control what can enter the brain from the bloodstream 

tight junctions of brain capillaries

prevent solute movement between endothelial cells

what kind of substances are permeable to the BBB?

small lipid-soluble molecules

general function of the spinal cord

to transmit sensory and motor content between the brain and the periphery 

four regions of the spinal cord

1. cervical

2. thoracis

3. lumbar

4. sacral 

dorsal root

carries sensory (afferent) information to CNS

ventral root

carries motor (efferent) information to muscles and glands

dorsal horn gray matter

1. receives sensory information from the body through dorsal roots

2. contains interneurons that process and integrate sensory signals

what does the ventral horn gray matter contain and what is its function?

1. contains motor neurons that send commands to muscles and glands

2. receives information from the brain 

ascending tracts of white matter

to the brain

descending tracts of white matter

from the brain

spinal reflex

initiates a response without input from the brain

cranial nerve I

1. olfactory 

2. sensory

3. smell information from nose 

cranial nerve II

1. optic

2. sensory

3. visual information from eyes

cranial nerve III

1. oculomotor 

2. motor

3. eye movement, pupil constriction, lens shape

cranial nerve IV

1. trochlear

2. motor

3. eye movement 

cranial nerve V

1. trigeminal

2. mixed 

3. sensory information from face, mouth; motor signals for chewing 

cranial nerve VI

1. abducens

2. motor

3. eye movement 

cranial nerve VII

1. facial

2. mixed

3. sensory for taste, efferent signals for tear and salivary glands, facial expression 

cranial nerve VIII

1. vestibulocochlear

2. sensory

3. hearing and equilibrium 

cranial nerve IX

1. glossopharyngeal

2. mixed

3. sensory from oral cavity, baro- and chemoreceptors in blood vessels, efferent for swallowing, parotid salivary gland secretion

cranial nerve X

1. vagus

2. mixed

3. sensory and efferents to many internal organs, muscles, and glands 

cranial nerve XI

1. spinal accessory

2. motor

3. muscles of oral cavity, some muscles in neck and shoulder 

cranial nerve XII

1. hypoglossal

2. motor

3. tongue muscles

where is the brainstem located?

between the brain and the spinal cord

main components of the brainstem

1. midbrain (colliculi)

2. pons

3. medulla oblongata 

target or source for the cranial nerves that deal with sensory and motor function in the head and neck

brainstem 

10/12 cranial nerves originate in…

the brainstem

cranial nerve nuclei

1. cluster of neurons in charge of processing and relaying sensory and motor information between the brain and structures in the head and neck

2. exist within the brainstem  

medulla white matter

1. ascending somatosensory tracts

2. descending corticospinal tracts 

medulla gray matter

1. brainstem nuclei that are responsible for involuntary functions

2. swallowing, vomiting, cardiorespiratory activity 

medulla location

transition between spinal cord to brain

pons general function

relay station for information transferred between the cerebellum and the brain

middle cerebellar peduncle

primary tract that carries information from the pons to the cerebellum 

neural cardiorespiratory control of the brainstem

pons and medulla collaboration 

where is the reticular activating system located?

pons

reticular activating system RAS

network of neural pathways in the pons that filters sensory information

what does the RAS control?

1. arousal and consciousness 

2. sleep-wake regulation

3. attention and focus 

4. emotion and pain modulation

midbrain

contains inferior and superior colliculi that regulate eye movements and auditory-vestibular reflexes 

diencephalon location

between the brainstem and the cerebrum

main components of diencephalon

1. hypothalamus

2. thalamus 

3. pineal gland

4. pituitary gland 

main idea of hypothalamus

maintaining homeostasis

what CNS structure controls the homeostasis of the following?: fight or flight, blood glucose, body temperature, osmolarity, reproductive functions, food intake, cardiovascular, hormones

hypothalamus

thalamus main idea

relay station, like a crossing guard

nuclei of the thalamus

1. relay nuclei: sensory information passes through on the way to the cortex

2. association nuclei: receives information from the cortex and projects back 

pituitary gland main word

hormones

posterior pituitary gland

stores and releases oxytocin and vasopressin