Anatomy lecture exam 4

Conduction

Nerve fibers conduct sensory and motor signals up and down the spinal cord

Neural integration

Spinal nerves receives info from many sources, integrate it, then gives a response.

Locomotion

Spinal cord contains central pattern generators that create a repetitive sequence of contraction

Reflexes

Involuntary responses to stimuli. Vital to posture, coordination, and protection.

Spinal cord

Arises from brainstem at the foramen magnum of skull. Cylinders of nervous tissue.

Spinal tract

Fibers with the same orgin, destination, and function

Ascending tract

Only in CNS. Myelinated bundles of axons that carry sensory information to brain stem/spinal cord

Descending tract

Only in CNS. Bundles of axons that carry motor information down

Contralateral

Destination is on the opposite side of the origin

Ipsilateral

Origin and destination on the same side (EX: Half of optic nerves)

Decussation

Crossing at the midline of tracts

First order neuron

Part of sensory tract. Carry sensory information from receptors to spinal cord

Second order neurons

Part of sensory tract. Carry information from the spinal cord to the thalamus

Third order neurons

Part of sensory nerves. Carry sensory info form the thalamus the postcentral gyrus in the cerebral cortex

Upper motor neurons

Part of motor tract. Carry motor info form the precentral gyrus in the cerebral cortex to the lower motor neuron.

Lower motor neuron

Part of motor tract. Carries motor info from the brainstem/spinal cord to the muscle or target organ.

Corticospinal tract

Carries signals from the cerebral cortex for precise, finely coordinated movements

Pyramids

Ridges on the anterior surface of the medulla oblongata. Formed from fibers decussating in lower medulla.

Nerve

Cord like bundle of axons found in the PNS. Axons are surrounded by schwann cells, neurolemma, and myelin sheath

Endoneurium

Loose connective tissue found around neurolemma

Perineurium

Connective tissue found around fascicles and overlap with squamous cells.

Epineurium

Dense irregular connective tissue found around entire nerve. Blood vessels penetrate.

Sensory(afferent) neurons

Carries signals from receptors to CNS

Motor(efferent) Neurons

Carries signals from the CNS to target muscles or glands

Posterior (dorsal) root

Carries sensory signals into the spinal cord

Posterior root ganglion

Contains neurosomas of sensory neurons that carry info to the spinal cord

Anterior(Ventral)root

Carries motor information out of the spinal cord

Cauda equina

Formed from root of L1-Co1. After the spinal cord, injections are done in their region to prevent spinal cord damage.

Anterior ramus

In thoracic region, gives rise to intercostal nerves. In others, come together to form plexuses.

Posterior ramus

Innervates muscles and joints in regions of the spine and back skin.

Meningeal branches

Reenter vertebral canal and innervates meninges, vertebrae, and spinal ligaments

Cervical plexus

In neck, C1-C5, supplies phrenic nerve to diaphragm

Brachial plexus

Near shoulder, C5-T1, supplies nerves to shoulder and neck. Contains median nerve, pinching nerve causes carpal tunnel syndrome

Lumbar plexus

L1-L4, lower back, supplies abdomen wall, anterior thigh, and genitalia.

sacral plexus

L4, L5, S1-S4. Supplies remainder of the lower trunk. Contains sciatic nerve-largest nerve.

Coccygeal plexus

S4, S5, Co1, supplies genitalia

Somatosensory function

Function of the plexuses. Carry sensory signals from bones, joints, muscles, and skin to spinal cord/brain

Proprioception

Function of the plexuses. Plexuses send info about the body’s position and movement from nerve ending in muscles, tendons, and joints.

Motor function

Function of plexuses. Stimulate muscle contractions

Dermatome

Specific area of a cutaneous region that innervated by a spinal nerve. Ex: C1 innervate part of neck. Regions overlap as much as 50 percent.

Dermatome map

Diagram of the cutaneous regions innervated by each nerve

Mixed nerves

Consist of both motor and sensory nerves. Can be somatic or viseral and General or special

Ganglion

Cluster of neurosoma outside the CNS. Enveloped in endoneurium continuous with the nerve/

31 pairs of spinal nerves

8 cervical, 1st nerve exits through skull, the rest leave through the intervertebral foramina

12 thoratic

5 lumbar

5 sacral

1 coccygeal

Rostral

To nose

Caudal

To tail end

Gray matter

Seat of the neurosomas, dendrites, and synapses. Dull in color due to lack of myelination. Forms surface layer of cerebral cortex, limbic system, and basal nuclei.

White matter

Bundles of axons. Lies deep to the gray matter. White due to myelination. Composed of tracts that connect parts of the brain together

Ventricle

4 internal chambers within the brain. 2 lateral ventricles, one in each hemisphere.

Intervertebral foramen

Tiny pores that connect to the third ventricle

Third ventricle

Narrow medial space beneath the corpus callosum.

Cerebral aqueduct

Below the third ventricle. Runs through mid brain

4th ventricle

Small triangular chamber between pons and cerebellum. Connects the central canal.

Central canal

Runs through spinal cord

Choroid plexus

Spongy mass of blood capillaries at the base of each ventricle

Ependymal cells

type of neuroglia that lines the ventricles and covers choroid plexuses. Produce the cerebral spinal fluid.

Cerebral spinal fluid

Clear colorless fluid that fills the ventricles and canals of the CNS. Subarachnoid space, endymal lining, and choroid plexus produces 500 mL a day.

Production of CSF

Begins with the filtration of blood plasma through capillaries in the brain. Ependymal cells modify and filtrate, making CSF more sodium and chloride then plasma.

Buoyancy

CSF allows brain to attain a considerable weight without being impaired by its own weight.

Protection

CSF protect the brain from colliding with the cranium. Knocking against the cranium can cause shaken baby syndrome and a concussion.

Chemical stability

Flow of the CNF removes metabolic waste form tissue and and regulate the chemical environment.

Median and lateral apertures

Where CSF flows after leaving the lateral ventricles

Subarachnoid space

CSF flows and bathes its external surface

Arachnoid villi

Where CSF is reabsorbed into the veneous blood of dural venous sinuses

Brain

Receives 15 percent of blood supply. 10 sec w/o blood flow=loss of consciousness. 1-2 min=significant brain damage. 4 min=irreversible brain damage.

Brain-barrier system

Regulates what substance go in and out of the brain. Blood can contain harmful materials. Guards the point of entry in the choroid plexuses.

Endothelial cells

Excludes harmful substances from entering the brain tissue while allowing nessecary material to pass through. Line capillaries

Blood CSF barrier

Protect the brain at the choroid plexuses. Forms tight junction between endothelial cells. Tight junctions are usally absent form endothelial cells. Allows exchange between CSF and blood tissue

Blood brain system

Highly permeable-water, glucose, and light solubles.

Slightly permeable-Sodium, potassium, chloride, and waste products.

Not permeable-Medications and drug treatments. Can be a barrier when creating.

Trauma and infection can damage the system leading to pathogens entering the brain tissue

Circumventricular organs

Places in the third and forth ventricle where the blood brain barrier is absent. Blood has direct access to the brain. Allows brain to monitor and respond to changes in blood glucose, Ph, osmolarity, and other variables. Can result in infections like HIV due to direct access

Reticular formation

Loose web of gray matter that runs vertically throughout the brainstem. Has connection with many area of the brain.

Somatic motor control in reticular formation

Voluntary control of muscles.

1) Adjusts muscle tension. Maintain muscle control, balance, and posture. Integrate visual, auditory, and stimuli into motor corrdination.

2) Gaze center-allows brain to track objects

3) Central pattern generators-neutral pools that produce rythmic signals to muscles that allow breathing and swallowing.

4) Cardiovascular control- Cardiac and vasomotor control

5) Pain modulators-Pain signals sent through reticular formation.

6) Sleep/conciuosness-Plays role in sleep and wake cycles

7) Hibituation- Activates system modulators activity in cerebral cortex to ignore inconsequential stimuli.

Cerebellum

Part of hindbrain, 2nd largest part of the brain. 2 hemispheres. Outer layer of gray matter with white matter on inside. Contains more then half the neurons in the brain. Highly important to motor coordination and locomotion . Has sensory, linguistic, emotional, and nonmotor function too.

Diencephalon

Contains epi, hypo, and thalamus. Encloses 2rd ventricle and most of brainstem.

Thalamus

2 ovoid masses of 23 nucleuses. Sits on top of the brainstem. Sends filters and sends signals to different areas of the cerebral cortex. Involves lymbic system

Limbic system

Complex structures including the cerebral cortex of the temporal and frontal lobe and some of anterior thalamic nuclei.

Hypothalamus

Form part of the wall and floor of the third ventricle. Extend anteriorly to optic chiasma. Each mamillary body contain 3-4 nuclei. Rely signals through the limbic system to the thalamus

Infundibulum

Stalk attaching pituitary gland to hypothalamus

Hypothalamic nuclei functions

Hormone secretions: Controls, anterior pituitary gland, regulating growth metabolism, reproduction and stress response

Autonomic functions: Major integrating center for autonomic responses like heart rate, blood pressure, gastrointestinal tract, and mobility

Thermoregulation: Controls internal body temp

Sleep/ wake cycle:

Food/water intake:

Memory

Emotions

Epithalamus

Pineal gland: Part of the endocrine system, secretes melatonin

Habenula: Relies signals from limbic system to midbrain. Thin roof over third ventricle

Cerebrum/telencephalon

Largest part of the brain, 2 hemispheres, origin of concioious thought, sensory perception, memory, and judgements. Where glia and myelinated nerves transmit signals

Corpus callosum

White fibrous tract that connects the hemispheres

Gyri/sulcus

increases the amount of cortex in cranial canal. Allows for more info processing in a smaller space. More of them mean smarter

Lobes

Named after the cranial bones. Many lobes over lap in function due to tract overlap.

Tracts

Bundles of axons in the CNS. 3 types: projection, association, and commissural.

Projection tract

Extend vertically and carry signals between high and low brain and the spinal cord. Ex: Corticospinal tract

Association tract

Connect different lobes of the same cerebral hemisphere together

Commissure tract

Cross cerebral hemispheres, allows for communication between two sides of cerebrum. Ex: Corpus callosum.

Neural integration

Carried out by gray matter in cerebrum.

Cerebral cortex

Covers surface of the hemispheres. 40% of the brains mass. 14-16 billion neurons. 90% is neocortex-6 layered tissue

Stellate cells

Spheroid neurosomas with dendrite in all directions. Receive sensory information on a local level with no axons.

Pyramidal cells

Tall cone shaped cells with apex toward brains surface. Thick dendrites with many branching, knobby axons. Only neuron that leaves the CNS.

Limbic system

Emotion/learning center. In each cerebral hemisphere. Connected through loss fibrous tracts

Cingulate gyrus

Arch over the corpus callosum

Hippocampus

In medial temporal lobe, have memory function.

Amygdala

In rostral part of the hippocampus, has emotion functions

Gratification

Sense of pleasure/reward

Aversion

Sense of sorrow/fear

Basal nuclei

Mass of gray matter inside white matter. Lateral to the thalamus. Receives input form the substantia nigra of mid brain and motor areas. Involved in motor control.

3 parts of basal nuclei

Caudate nucleus, Putamen, and globus pallidus.