Nervous Tissue, Brain, Spinal Cord and Nerves

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Neuron

- nerve cell
- excitable cells that transmit electrical
signals
- Cells are long-lived, amitotic, and have
high metabolic rate (meaning high oxygen and glucose needs)

Cell Body

contains the nucleus and metabolic center of the
cell, has a lot of rough ER

Nucleus

membrane-bound structure found in the soma or body of the neuron and contains the nucleolus

Neurofibrils

one of the delicate threads running in every direction through the cytoplasm of a nerve cell and extending into the axon and dendrites; believed to be neurofilament bundles, and perhaps neurotubules.

Nissl Bodies

rough ER of neuron

Dendrites

conduct impulses toward the cell body

Axon

conduct impulses away from the cell body

Axon Hillock

cone-shaped area from which axons arise

Axon Terminals

contain vesicles that contain neurotransmitters

Synaptic Cleft

gap between adjacent neurons

Schwann Cells

cells that wrap around axon like a jelly roll, form myelin sheath

Myelin Sheath

a white fatty material that insulates and protects the fibers and speeds up nerve impulse transmission

Neurolemma

the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral nervous system.

Endoneurium

a layer of delicate connective tissue that encloses the myelin sheath of a nerve fiber within a fasciculus.

Nodes of Ranvier

gaps in myelin sheath along the axon

Synapses

A) axodendritic
B) axosomatic
C) axoaxonic

Vesicles

In a neuron they store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel.

Presynaptic Membrane

The part of the cell membrane of an axon terminal that faces the cell membrane of the neuron or muscle fiber with which the axon terminal establishes a synapse.

Postsynaptic Membrane

The surface of the cell on the opposite side of the synapse from the synaptic terminal of the stimulating neuron that contains receptor proteins and degradative enzymes for the neurotransmitter.

Voltage gated calcium channels

mediate calcium influx in response to membrane depolarization and regulate intracellular processes such as contraction, secretion, neuro-transmission, and gene expression. Their activity is essential to couple electrical signals in the cell surface to physiological events in cells.

Cerebrum

80% of Brain mass
-paired (left and right hemispheres)
-made up of the frontal lobe, parietal lobe, temporal lobe, occipital lobe, insula.

Cerebrum: Frontal Lobe

* Motor Functions
* Higher Order Functions
* Planning
* Reasoning
* Judgement
* Impulse Control
* Memory

Frontal Lobe: Broca's Area

In frontal lobe, located in one hemisphere only, usually left.
- allows you to form the words that you want to say
- motor speech
- Damage here can lead to Expressive Aphasia: the loss of the ability to produce language (spoken or written).

Frontal Lobe: Premotor Area

- Located anterior to the precentral gyrus of frontal lobe
- Controls learned, repetitious, or patterned motor skills such as playing musical instrument, helps in planned movements

Frontal Lobe: Prefrontal Cortex

- intellect, judgement, etc
- Working memory for spatial tasks
- Executive area for task management
- Working memory for object-recall tasks
- Solving complex, multitask problems

Frontal Lobe: Primary motor cortex

- area of the frontal cortex just anterior to the central sulcus
- allows conscious control of voluntary contra-lateral movement of skeletal muscles

Cerebrum: Parietal Lobe

can be divided into two functional regions. One involves sensation and perception and the other is concerned with integrating sensory input, primarily with the visual system. The first function integrates sensory information to form a single perception (cognition).

Parietal Lobe: Primary Somatosensory cortex

Located in the postcentral gyrus, this area:
- Receives information from the skin and skeletal muscles and identify region being stimulated

Parietal Lobe: Association Somatosensory Cortex

Located posterior to the primary somatosensory cortex
- Integrates sensory information such as temp., pressure... relayed by the primary somatosensory cortex

Cerebrum: Temporal Lobe

associated with hearing
- coordinate auditory and visual aspects of language

Temporal Lobe: Primary Auditory area

Located at the temporal lobe:
- allows you to hear
- Determines pitch, rhythm, and loudness

Temporal Lobe: Wernicke's area

- usually on left side of the Temporal Lobe
- allows you to understand what is being said
- damage here leads to Receptive Aphasia: the inability to comprehend language or speak with appropriately meaningful words

Temporal Lobe: Olfactory area

- deep in the brain: Insula
- smell

Cerebrum: Occipital Lobe

Vision
- contains primary visual cortex and visual association area

Occipital Lobe: Primary Visual cortex

- allows you to see
- most posterior tip of the occipital lobe

Occipital Lobe: Visual Association cortex

anterior to primary visual cortex
- Surrounds the primary visual cortex
- Interprets visual stimuli (e.g., color, form, and movement) using past experiences

Cerebrum: Insula

- deep in the brain
- gustatory (taste)

Gyri

- gyrus: elevated ridge (wrinkle of the brain)
- increases surfaces area

Precentral Gyrus (Motor Strip)

the location of primary motor cortex, the main area for control of precise, skilled, voluntary movements

Postcentral Gyrus (Somatosensory Strip)

the location of primary somatosensory cortex, the main sensory receptive area for the sense of touch

Sulci

sulcus: groove (gap between wrinkles)

Central Sulcus

separates frontal lobe from parietal lobe

Lateral Sulcus

separates temporal lobe from parietal and frontal lobes

Fissures

deep groove
- separates lobes

Longitudinal Fissure

separates left and right hemispheres of cerebrum

Transverse Fissure

separates cerebrum and cerebellum

Corpus Callosum

a commissure
- the largest commissure in the brain ("C" shaped in mid sagittal view)

Commissure

connect corresponding gray areas of the two hemispheres

Fornix

a C-shaped bundle of axons in the brain, and carries signals from the hippocampus to the mammillary bodies

Septum Pellucidum

thin membrane that separates lateral ventricles

Hippocampus

- part of the limbic system
- plays important roles in long-term memory and spatial navigation.
- located inside the medial temporal lobe, beneath the cortical surface.

Diencephalon

the region of the brain that includes the thalamus, hypothalamus and epithalamus

Olfactory Bulbs

- located on the inferior (bottom) side of the brain. The olfactory bulb is supported and protected by the cribriform plate of the ethmoid bone.

- Relays Sensory Signals to the Olfactory Tract
- Sense of Smell

Olfactory Tracts

a bundle of axons connecting the cells of the olfactory bulb to several target regions in the brain.

Optic Nerves

CN 2

Optic Chiasma

is the part of the brain where the optic nerves (CN II) partially cross. The optic chiasm is located at the bottom of the brain immediately below the hypothalamus.

Pituitary Gland

an endocrine gland about the size of a pea. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica).

Diencephalon: Thalamus

- Relay Station
- Paired, egg-shaped masses that form the superolateral walls of the third ventricle
- Connected at the midline by the intermediate mass

Mammillary Bodies

- on the ventral side of brain under optic chiasm and pituitary location.
- are involved with the processing of recognition memory. They are believed to add the element of smell to memories.

Diencephalon: Hypothalamus

- Forms the inferolateral walls of the third ventricle
- Role in ANS: Regulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing, and many other visceral activities
- Maintains normal body temperature
- Major role in body's water balance
- Endocrine Functions of the Hypothalamus: produce ADH and oxytocin
- Regulates feelings of hunger and satiety
- Regulates sleep and the sleep cycle
- Perception of pleasure, fear, and rage

Infundibulum

AKA pituitary stalk
- the connection between the hypothalamus and the posterior pituitary

Diencephalon: Epithalamus

Epithalamus- forms roof of the third ventricle.

- Found in epithalamus area are:
1. Pineal gland - extends from the posterior
border and secretes melatonin
Melatonin - a hormone involved with sleep regulation, sleep-wake cycles, and mood
2. Choroid plexus - a structure that secretes cerebral spinal fluid (CSF)

Choroid Plexus

a structure that secretes cerebral spinal fluid (CSF)

Pineal Body (gland)

extends from the posterior border and secretes melatonin

Brain Stem

midbrain, pons, medulla oblongata

- Similar to spinal cord but contains embedded
nuclei
- Controls automatic behaviors necessary for survival
- Provides the pathway for tracts between higher and lower brain centers
- Associated with 10 of the 12 pairs of cranial nerves

Brain Stem: Midbrain

- Located between the diencephalon and the pons
- Midbrain structures include:
- Cerebral peduncles - two bulging structures that contain descending pyramidal motor tracts
- Cerebral aqueduct - hollow tube that connects the third and fourth ventricles

Midbrain: Cerebral Peduncles

two bulging structures that contain descending pyramidal motor tracts

Midbrain: Corpora Quadrigemina

four dome like protrusions of the dorsal midbrain
made up of:
- Superior colliculi - visual reflex centers
- Inferior colliculi - auditory relay centers

Corpora Quadrigemina: Superior Colliculi

visual reflex centers

Corpora Quadrigemina: Inferior Colliculi

auditory relay centers

Brain Stem: Pons

- Bulging brainstem region between the midbrain and the medulla oblongata
- Forms part of the anterior wall of the fourth
ventricle
- Regulates pattern of respirations
Fibers of the pons:
- Connect higher brain centers and the spinal cord
- Relay impulses between the motor cortex and the cerebellum

Brain Stem: Medulla Oblongota

Joins spinal cord at foramen magnum
Contains heart rate, blood pressure , breathing rate centers and vomiting and cough centers , Swallowing , Sneezing,
Hiccuping
- Forms part of the ventral wall of the fourth ventricle
Contains:
- a choroid plexus of the fourth ventricle
- Pyramids
- Decussation

Medulla Oblongota: Pyramids

large corticospinal tracts descending from the motor cortex

Medulla Oblongota: Decussation of Pyramids

Tracts cross over to the opposite side before entering the spinal cord. Cerebral hemisphere control voluntary movements of muscles on the opposite side of the body

Cerebellum

BALANCE and COORDINATION center
- Two hemispheres connected by vermis
- Protrudes under the occipital lobes of the cerebrum
- Makes up 11% of the brain's mass
- Each hemisphere has three lobes
- Arbor vitae - distinctive treelike pattern of the cerebellar white matter
All fibers in the cerebellum are ipsilateral

Cerebellum: Flocculus

# 5's
At its base, it receives input from the middle ears vestibular system and regulates balance

Cerebellum: Vermis

a narrow, wormlike structure between the hemispheres of the cerebellum

Cerebellum: Arbor Vitae

distinctive treelike pattern of the cerebellar white matter

Cerebellum: Peduncles

(A) Superior Peduncle (B) Middle Peduncle (C) Inferior Peduncle
- Three paired fiber tracts that connect the cerebellum to the brain stem
- All fibers in the cerebellum are ipsilateral
- Superior peduncles connect the cerebellum to the midbrain
- Middle peduncles connect the pons to the cerebellum
- Inferior peduncles connect the medulla to the cerebellum

Ventricles

cavities in brain that are filled with cerebrospinal fluid

Lateral Ventricles:

C-shaped , deep within cerebral hemispheres

3rd Ventricle

found in the diencephalon and communicates with lateral ventricles via intraventricular foramen

4th Ventricle

dorsal to the pons and in front of cerebellum. Continuous with 3rd ventricle via cerebral aquaduct
- openings (apertures) in the wall of the this connect the ventricles with the subarachnoid space surrounding the brain

Ventricles: Cerebral Aqueduct (aqueduct of Sylvius):

hollow tube that connects the third and fourth ventricles

Ventricles: Choroid Plexus

a structure that secretes cerebral spinal fluid (CSF)

Ventricles: Foramen of Munro (interventricular)

channels that allow cerebrospinal fluid (CSF) produced in the lateral ventricles to reach the third ventricle and then the rest of the brain's ventricular system.

Cervical Enlargement

site where nerves serving the upper limbs emerge

Lumbar Enlargement

site where nerves serving the lower limbs emerge

Conus Medullaris

terminal portion of the spinal cord

Cauda Equina

collection of nerve roots at the inferior end of the vertebral canal

Filum Terminale

fibrous extension of conus medullaris that extends to coccyx where it anchors the spinal cord
- Protected by vertebrae, meninges, and CSF

Posterior Horn

interneurons that receive somatic and visceral sensory input

Anterior Horn

somatic motor neurons whose axons exit the cord via ventral roots

Lateral Horn

(only in thoracic and lumbar regions)
- sympathetic neurons

Gray Commissure

a thin strip of gray matter that surrounds the central canal of the spinal cord and, along with the anterior white commissure, connects the two halves of the cord.

Central Canal

The small canal running through the center of the spinal cord from the conus medullaris to the lower part of the fourth ventricle; represents the embryonic neural tube.

Posterior Funiculus

the white matter of the spinal cord lying on either side between the posterior median sulcus and the dorsal root.
- This area includes the dorsal columns (also called the posterior columns) which contains the fasciculus gracilis and, higher in the body, the fasciculus cuneatus
- ascending tracts

Anterior Funiculus

white matter of the spinal cord lying on either side between the anterior median fissure and the ventral root.

Lateral Funiculus

the white matter of the spinal cord lying on either side between the anterior median fissure and the ventral root.

Posterior Median Sulcus

a shallow vertical groove dividing the spinal cord throughout its whole length in the midline posteriorly.

Anterior Median Fissure

a groove along the anterior midline of the spinal cord that incompletely divides it into symmetrical halves

Dorsal Root

s arise from sensory neurons in the dorsal root ganglion and contain sensory (afferent) fibers

Sympathetic Chain Ganglia

- bilaterally symmetric and located just ventral and lateral to the spinal cord. They extend from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
- delivers information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response.

Dorsal Root Ganglion

a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves.

Ventral Root

arise from the anterior horn and contain motor (efferent) fibers

Spinal Nerve

Thirty-one pairs of mixed nerves arise from the spinal cord and supply all parts of the body except the head
- They are named according to their point of origin
 8 cervical (C1-C8)
 12 thoracic (T1-T12)
 5 Lumbar (L1-L5)
 5 Sacral (S1-S5)
 1 Coccygeal (C0)

Cervical Plexus

The cervical plexus is formed by ventral rami of C1-C4
- Supplies skin and muscles of the neck, ear, back of head, and superior parts shoulders
- The most important nerve of this plexus is the phrenic nerve
- The phrenic nerve is the major motor and sensory nerve of the diaphragm (receives fibers from C3-C5)

Brachial Plexus

- Formed by C5-C8 and T1(C4and T2may also contribute to this plexus)
- Supplies shoulders and upper limbs

Lumbar Plexus

Arises from L1-L4
- Innervates the thigh, abdominal wall, and and external genitals
- Femoral nerve—innervates quadriceps and skin of anterior thigh and medial surface of leg
- Obturator nerve—passes through obturator foramen to innervate adductor muscles

Sacral Plexus

Arises from L4-S4
- Serves the buttock, lower limb, pelvic structures, and perineum

Phrenic nerve

The phrenic nerve is the major motor and sensory nerve of the diaphragm (receives fibers from C3-C5)

Intercostal Nerves

supply muscles of the ribs, anterolateral thorax, and abdominal wall

Axillary Nerve

innervates the deltoid, teres minor, and skin and joint capsule of the shoulder

Musculocutaneous Nerve

innervates the biceps brachii and brachialis and skin of lateral forearm

Median Nerve

innervates the skin, most flexors and pronators in the forearm, and some intrinsic muscles of the hand

Radial Nerve

innervates essentially all extensor muscles, supinators, and posterior skin of limb

Ulnar Nerve

supplies the flexor carpi ulnaris, part of the flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand

Femoral Nerve

innervates quadriceps and skin of anterior thigh and medial surface of leg

Saphenous Nerve

is the largest cutaneous branch of the femoral nerve.

Obturator Nerve

passes through obturator foramen to innervate adductor muscles

Lateral Femoral Cutaneous Nerve

a cutaneous nerve that innervates the skin on the lateral part of the thigh.
L3

Ilioinguinal Nerve

a branch of the first lumbar nerve (L1). It separates from the first lumbar nerve along with the larger iliohypogastric nerve.
- a branch of the first lumbar nerve that is distributed to the muscles of the anterolateral wall of the abdomen, to the skin of the proximal and medial part of the thigh, and to the base of the penis and the scrotum in the male or the mons veneris and labia majora in the female

Sciatic Nerve

Longest and thickest nerve of the body
- Innervates the hamstring muscles, adductor magnus, and
most muscles in the leg and foot
- The sciatic is actually Composed of two nerves: tibial and
common fibular ( peroneal) nerves

Tibial Nerve

a branch of the sciatic nerve that passes through the popliteal fossa to pass below the arch of soleus.

Sural Nerve

(short saphenous nerve) lies with the small saphenous vein. It supplies the branches to the skin on the back of the leg and then continues as the "lateral dorsal cutaneous nerve" along the outside of the foot and little toe

Pudendal Nerve

supplies most of nerves in perineum.

Common Peroneal/Fibular Nerve (Deep Branch)

travels in the anterior compartment of the leg on the anterior surface of the interosseous membrane (it travels with the anterior tibial artery).
- provides motor innervation to the muscles of the anterior compartment of the leg (muscles that primarily dorsiflex the foot and extend the toes).

Common Peroneal/Fibular Nerve (Superficial Branch)

arises from the common fibular nerve near the neck of the fibula.
- it travels in the lateral compartment of the leg.
- provides motor innervation to the muscles of the lateral compartment of the leg (muscles that evert the foot).
- provides sensory innervation to the anterolateral aspect of the leg (the distal half) and the dorsum of the foot (the exception is the webspace between the hallux and second digit).

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