organization of the nervous system & spinal reflexes

human anatomy and physiology lecture 6

cranial nerves

peripheral nerves connecting to the brain

spinal nerves

peripheral nerves attached to the spinal cord

cerebrum

conscious thought process, memory storage and processing, regulation of skeletal muscle contractions

diencephalon

region of the brain containing the thalamus and hypothalamus

thalamus

relays and filters sensory information

hypothalamus

controls emotions, autonomic functions, and hormone production

brainstem

region of the brain containing the medulla oblongata

medulla oblongata

relays information, autonomic center for regulation of visceral function

cerebellum

coordinates complex motor somatic patterns, adjusts output of other somatic motor centers in brain and spinal cord

spinal cord

carries sensory and motor information between the brain and other parts of the body

meninges

membrane around the spinal cord

afferent division

communicates incoming sensory signals

somatic stimuli

external stimuli

visceral stimuli

internal stimuli

efferent division

communicates outgoing motor signals

somatic signals

sent to voluntary effectors

autonomic signals

sent to involuntary effectors

sympathetic signal

mobilizes body systems, fight-or-flight

parasympathetic signal

conserves energy, rest-and-digest

major functions of the nervous system

• monitor internal and external environments

• integrate sensory information

• coordinate responses from all organ systems

major cell types of nervous tissue

neurons and neuroglial cells

neurons

specialized for the propagation of electrical signals for communication; do not divide in adults

neuroglial cells

support the neurons by regulating the neuronal environment, protecting the neurons from mechanical trauma or infectious threats, and providing a physical framework for the neurons; divide as needed

sensory neurons

collect sensory information and transport them to the central nervous system, commonly unipolar

association or interneurons

connect sensory and motor neurons inside the central nervous system, commonly multipolar

motor neurons

transmit motor information towards the peripheral nervous system, commonly multipolar

ganglia

structures into which the cell bodies of sensory neurons cluster

mechanoreceptors

detect touch, pressure, vibrations

photoreceptors

detect light

chemoreceptors

detect the presence of a chemical

nociceptors

detect pain

proprioceptors

detect the degree of stretch in a muscle

endocrine

release products directly into the bloodstream

exocrine

release products onto epithelial tissue via a duct

neuroglia in the central nervous system

• astrocytes

• oligodendrocytes

• microglia

• ependymal cells

neuroglia in the peripheral nervous system

• satellite cells

• Schwann cells

grey and white matter in the cerebrum

grey matter occurs superficially while the white matter occurs deeper

grey and white matter in the spinal cord

grey matter occurs deep (butterfly shape) while the white matter occurs superficially

grey matter in the brain

cerebral cortex (superficial layer) and basal nuclei (deeper structures)

grey matter in the spinal cord

dorsal (posterior) horn, lateral horn, and ventral (anterior) horn

dorsal (posterior) horn

receive sensory information

lateral horn

receive autonomic motor information

ventral (anterior) horn

receive somatic motor information

white matter in the spinal cord

posterior (dorsal) column, lateral column, anterior (ventral) column

posterior (dorsal) column

generally sensory information

anterior (ventral) column

generally motor information

tract

bundle of axons bunched up together in the central nervous system

nerve

bundle of axons wrapped in connective tissue found in the peripheral nervous system

posterior root

end of spinal nerve for sensory information

anterior root

end of spinal nerve for motor information

ganglion

collection of neuron bodies found in the peripheral nervous system

reflex

fast, predictable response to a stimulus

spinal reflex

simple, subconscious, without involvement of the brain

steps of a reflex arc

1. arrival of a stimulus and activation of a receptor

2. activation of a sensory neuron

3. information processing

4. activation of a motor neuron

5. response of a peripheral effector