Lab 11: Nervous Tissue & Spinal Cord

Define homeostasis

Ability of the body to maintain a stable environment in response to internal & external stimuli

The CNS includes

Brain & spinal cord

The PNS includes

Cranial/spinal nerves, ganglia, & sensory receptors

The CNS processes

Information received by the PNS receptors, controls the actions of all parts of the body, & is a site of thoughts, emotions, & memory

Function of neurons

Impulse conduction & for special attributes; thinking, muscle activity & regulating glands

Function of dendrites

Carries graded potentials towards soma; mechanical & ligand gated

Function of cell body (soma)

Contains nucleus & organelles; ligand gated

Function of axon

Propagates nerve impulses toward another neuron, muscle, or gland

The axon hillock

Joins cell body to the soma

The axon collateral is

Along the length of an axon, branches off

The axon terminal is

End of axon dividing into processes

The synaptic end contains

Synaptic end bulbs exhibiting varicosities with synaptic vesicles

Function of myelin sheath

Electrically insulates axon of a neuron increasing velocity of action potential propagation

What is the neurolemma

Cytoplasmic layer of Schwann cell

Nodes of Ranvier are

Space along myelinated axon between Schwann cells

Neurons are classified as;

Multipolar, bipolar, & unipolar

Where are multipolar neurons found

All motor, most interneurons

Where are bipolar neurons found

Retina, inner ear, olfactory

Where are pseudounipolar neurons found

Sensory receptors

What is the neuromuscular junction?

Synaptic connection between the terminal end of a motor nerve & a muscle

Functions of neuroglia

Structural support for neurons, forming myelin sheaths, engulfing microorganisms & cell debris, and forming cerebrospinal fluid

Function of astrocytes

Structural support, blood-brain barrier, formation of neural synapse, & regulation for ion/neurotransmitter concentration

Function of oligodendrocytes

Forms & maintains myelin sheath

Function of microglia

Immune cell, phagocytic

Function of ependymal cells

Produces CSF, blood-CSF barrier

Function of Schwann cells

PNS; encloses axon (20) or forms myelin sheath (1), helps with axon regeneration

Function of satellite cells

Surrounds ganglia, structural support, & regulate exchange of materials

Difference between neurons & neuroglia

Neurons are electrically excitable (nerve impulses & neuroglia are for support, protection, & can undergo mitotic division

Where does the spinal cord extend to & from

Medulla oblongata to L2

White matter in the spinal cord carry

Sensory information to the brain, & motor information to the PNS

Grey matter in the spinal cord contains

Cell bodies & axons of interneurons

The spinal cord carries impulse propagation from the

PNS to the brain, & the brain to various effectors

Function of the spinal meninges

Connective tissue that protect & cushion the spinal cord; continuous with the cranial meninges

Superficial layer of the spinal meninges

Dura mater; dense irregular connective tissue, toughest

Middle layer of the spinal meninges

Arachnoid mater; collagen & elastin fibers

What is between the dura & arachnoid mater?

Subdural space; interstitial fluid

Deepest layer of the spinal meninges

Pia mater; blood vessels

What is between the vertebral column & the dura mater?

Epidural space; fat & connective tissue

What is between the arachnoid & pia mater?

Subarachnoid space; cerebrospinal fluid

Grey matter in the spinal cord contains

Unmyelinated axons, dendrites, nuclei, neuroglia; integration (EPSP, ISPS)

Anterior horn of the spinal cord is for

Somatic motor nuclei to effector

Posterior horn of the spinal cord contains

Axons of sensory neurons & interneurons

White matter in the spinal cord contains

Bundles of myelinated axons, sensory/motor tracts

Spinal nerves are

Bundles of axons outside the CNS, connects CNS to sensory receptors & effectors

Central canal contains

CSF

Axons exiting spinal cord form

Rootslets which form roots

Anterior root of the spinal cord is for

Motor axons (efferent)

Posterior root of the spinal cord is for

Sensory axons (afferent)

Anterior & posterior root merge together and form a

Mixed nerves; both sensory & motor functions

Ganglia in the spinal cord contains

Cell bodies of sensory neurons

Anterior median fissure

Separates the anterior of the spinal cord

Posterior median sulcus

Separates posterior of the spinal cord

Filum terminale

Extension of the pia mater & anchors spinal cord to coccyx; “horse tail”

The spinal nerves exit through the

Intervertebral foramina

What is a nerve

Bundle of axons from multiple neurons; PNS

The anterior spinal nerves divide into branches called

Rami

The anterior rami form a complex network of motor nerves called

Plexus

What spinal nerves are not included in the anterior rami

Thoracic spinal nerves

What are reflexes

Rapid, automatic sequences that occur in response to a stimuli; maintains homeostasis

Components of a reflex arc;

Receptor, sensory neurons, integrating center, motor neuron, & effector

The integrating centers are either in

The spinal cord or the brain

Reflexes in smooth or cardiac muscle are called

Autonomic/visceral reflexes

Examples of autonomic/visceral reflexes

Digestion, blood pressure, salivation, & sweating

What are stretch reflexes

The effector muscle is the same muscle as the one being stimulated

What are receptors involved in a reflex arc?

Baroreceptors, chemoreceptors, mechanoreceptors

What are effectors involved in a reflex arc?

Skeletal, smooth, cardiac muscle, & glands

Give an example of a reflex

Paterllar reflex: strike patellar tendon with rubber mallet, observe movement of the leg

Plantar flexion: run a blunt end from the heel along the outer edge of the foot towards the big toe, observe movement of the toes

What is the difference between a monosynaptic & a polysynaptic

Monosynaptic is 1 synapse (sensory to motor), while polysynaptic is more than 1 (sensory to interneuron to motor)

How can the reflexes tested be used for diagnostic purposes?

Can be a test to see if there are any abnormalities in the nerves