Module 3: Control and Coordination

Dendrites

shorter, more numerous, receive information, converts chemical signals into electrical signals

Cell body

integrates electrical signals; contains the nucleus and other cell organelles 

Axon

Single long fibers, conducts electrical signals away from the cell

Chromatophilic substance

Rough ER; transport system

Myelin

insulation surrounding axons

Nodes of Ranvier

gaps in the insulation

Multipolar neurons

contains the axon and two or more dendrites in the CNS (brain & spinal cord) (motor neurons, most CNS neurons)

Unipolar neurons

have only one process; have an axon that emerges from the cell body (sensory neurons in PNS)

Bipolar neurons

have two processes; one is the axon and one the dendrite (retina, olfactory epithelium)

Anaxonic neurons

lack an axon (interneurons in brain)

Sensory (afferent) neurons

receive sensory input from the environment and transmit it to the CNS

Interneurons

facilitates communication between other neurons/determines where information is sent

Motor (efferent) neurons

transmits signals from the CNS to muscles, enabling movement 

Graded potentials

wave of electrical excitation proportional to the magnitude of the stimulus that triggers it

Action potentials

all-or-nothing response

Synapses

gaps between junctions of neurons where neurotransmitters are released 

Convergence (summation)

Multiple signals merge into a single pathway

Divergence (distribution)

a single neuron branching out to communicate with many other neurons

Inhibition

The process of reducing or preventing a neuron from firing an impulse

Evolutionary pressures related to brain expansion and bipedal locomotion influenced changes in human skull and pelvic anatomy & trade-offs between the skeletal and nervous systems

• Larger brains were an advantage for social interactions in unpredictable environment

• Narrowing of the pelvis favored delayed fusion of the metopic suture, allowing for massive increase in brain size during early life

• Human brains grow rapidly before birth through the first year and into childhood

Neuroglial cells

support, nourish and insulate neurons; they guide neuron development and regulate chemical communication

Microglia

• ovoid-shaped cells with high branched, narrow cell processes

• immune function; digest debris, kills bacteria

• Provide protection for the brain and spinal cord

Oligodendrocytes

• Make myelin sheath that provides insulation around the axons

• Found in the CNS

Astrocyte

• Star-shaped glia 

• Connect blood vessels to neurons; Maintain blood-brain barrier

• Nutrient supply

Ependymal cells

• Forms membranes around tissues 

• Line the ventricles of the brain and spinal cord

• Assist in producing, monitoring, and circulating CSF

• form blood-CSF barrier

Schwaan cells

Form the insulating myelin sheath around the neurons in the PNS

Multiple Sclerosis (MS)

An autoimmune disease where myelin sheath is damaged or demyelination (gaps or loss of myelin sheath)

Multiple Sclerosis (MS) Causes

• Conduction can be slowed or blocked causing impaired communication between neurons

• Nerves are unable to send or receive signals

Multiple Sclerosis (MS) Symptoms

• Weakness or numbness in the limbs

• Difficulty walking or coordinating movement 

• Burning sensations

Cerebrum

• wrinkly large part of the brain 

• high mental function, solving problems

Cerebellum

• balance and coordination 

• white matter within gives it a tree-like appearance (arbor vitae)

Diencephalon

Primary relay and processing center for sensory information and autonomic control 

Brainstem

regulates visceral functions 

Fissures

deep groove

Sulcus

shallow groove 

Gyrus

 bumps

Frontal lobe

executive functions; Associated with decision-making, problem-solving, and planning

Parietal lobe

perception, sense-making, math; Processes sensory information like touch, temperature, and pain.

Occipital lobe

Primary region for visual processing

Temporal lobe

Important for auditory processing and memory.

Corpus callosum

 connects the two hemispheres 

• The left side of the brain controls the right side of the body!

Thalamus

relays sensory and motor information from various locations to the cerebral cortex; regulates consciousness, sleep, and alertness

Hypothalamus

maintain homeostasis by controlling blood pressure, thermoregulation, and our sleep-wake cycle

Midbrain

 visual reflexes, eye movements

Pons

relay sensory information

Medulla

heart, respiration, blood pressure 

Limbic system

behavior and emotional response

• amygdala and hippocampus

Amygdala

• storage of memories associated with emotion

• Also associated with fear response and aggression

Hippocampus

• (“sea horse”)

• storage and retrieval of memories

Cervical enlargement

• (C5 - T1)

  • Increased number of nerves needed to supply the upper limbs

Lumbar enlargement

• (T11 - L2)

  • Widened area of the spinal cord that gives attachment to the nerves which supply the lower limbs

Conus medullaris

• Cone shaped terminal portion of the spinal cord

• Provide all motor and sensory innervation to lower limbs

Cauda equina

Send and receive messages between the lower limbs and the pelvic organs

Grey matter

made up of the cell bodies of neurons

White matter

consists of axons

Dorsal horn (spinal cord)

contains neurons that receive somatosensory information from the body

Ventral horn (Cross-sectional of spinal cord)

contains motor neurons that exit the spinal cord to innervate skeletal muscle

Lateral horn (spinal cord)

contains neurons that innervate visceral and pelvic organs

Alzheimer’s disease

 a neurodegenerative disease and is the most common form of dementia

Alzheimer’s disease causes

• Amyloid proteins build up in brain cells and form plaques.

• Another protein, tau, twists into tangles.

• These plaques and tangles eventually lead to the death of cells because they prevent the cells from sending signals and carrying out their normal function. 

• The hippocampus is one of the first areas affected 

Alzheimer’s disease symptoms

forgetting words or names, misplacing objects, trouble planning/organizing, trouble with simple tasks

Cranial nerve I

• Olfactory 

• Sensory 

• Sense of smell

Cranial nerve II

• Optic

• Sensory

• Transmits information from the eye’s retina. Vision.

Cranial nerve III

• Oculomotor

• Motor

• Controls most of the muscles of the eye (extrinsic and intrinsic) Moves the eyeball and constricts pupils

Cranial nerve IV

• Trochlear

• Motor

• Innervates an extrinsic eye muscle, eyelid. Moves eye downward and outward.

Cranial nerve V

• Trigeminal

• Sensory and motor 

• The main sensory nerve of the face. It controls chewing muscles.

Cranial nerve VI

• Abducens

• Motor 

• Controls one of the eye muscles (lateral rectus). Moves eye outward.

Cranial nerve VII

• Facial

• Sensory and motor

• Innervates the muscles of facial expression

• Controls taste (front 2/3 of tongue)

Cranial nerve VIII

• Vestibulocochlear

• Sensory

• Hearing and balance (also called auditory nerve)

Cranial nerve IX

• Glossopharyngeal 

• Sensory and motor

• Taste, swallowing, speech, and salivation

Cranial nerve X

• Vagus 

• Sensory and motor

• Innervates all of the organs in the thoracic and abdominal cavities

Cranial nerve XI

• Accessory

• Motor

• It just supplies the shoulder muscles 

Cranial nerve XII

• Hypoglossal 

• Motor

• Speech, swallowing, and chewing

Rami

 branches of a spinal nerve

Ventral rami (Spinal Nerve)

 (larger) innervate the ventral and lateral portions of the trunk, and limbs

Dorsal Rami (Spinal Nerve)

(smaller) innervate deep muscle and skin of the back 

Dorsal ganglion (spinal nerve)

contain only sensory cell bodies only

Dorsal root (Spinal Nerve)

contain sensory axons only

Ventral root (spinal nerve)

contain motor axons only 

Plexuses

main portions of the spinal nerves combine to form complex networks

Cervical plexus

• most branches are cutaneous nerves that supply sensory impulses from the skin of the neck, ear, back of the head and shoulders

  • Phrenic nerve

Phrenic nerve

sole motor nerve supply to the diaphragm for breathing 

Brachial Plexuses

• Suprascapular nerve 

• Axillary nerve

• Radial nerve

• Median nerve 

• Ulnar nerve 

Lumbar plexus

• Femoral nerve

• Obturator nerve

Sacral plexus

• Sciatic nerve

• Pudendal nerve 

Sciatic nerve

supplies the entire lower limb (leg) except anteromedial thigh

Shingles

a viral infection that causes a painful rash

Shingles Causes

It is caused by the varicella-zoster virus (VZV), the same virus that causes chicken pox.

Shingles Symptoms

Pain, burning, tingling, or numbness in a localized area, usually on one side of the body or face. Red bumps that appear in a cluster or line. 

Shingles relationship to cranial and spinal nerves

After primary infection (chickenpox), the virus lies dormant in neurons, including the cranial nerve ganglia and dorsal root ganglia. Once reactivated, the virus follows a dermatome, an area of the skin where the sensation is supplied by one spinal nerve.

• The trigeminal nerve (V), facial nerve (VII), and vestibulocochlear nerve (VIII) are frequently involved in shingles cases.

Meninges

membranes located between bone and soft tissue

• Dura mater

• Arachnoid

• Pia mater 

Cerebral spinal fluid (CSF)

clear liquid surrounding brain and spinal cord; cushions the brain; can be used in diagnostics with a lumbar puncture It protects the brain by acting as a shock absorber.

Pituitary gland

• Location: Brain

• Function: Releases hormones that control other glands

Thyroid gland

• Location: Throat

• Function: Releases hormones that help control metabolism

Parathyroid Gland

• Location: Throat 

• Function: Releases hormones that control level of calcium in blood

Adrenal Gland

• Location: Above kidneys

• Function: Releases hormones that control stress response

Pineal Gland

• Location: Brain

• Function: Releases hormones that control sleep-wake cycles

Pancreas

• Location: Under stomach 

• Function: Releases hormones to maintain blood sugar

Testes

• Location: Lower abdomen/groin

• Function: Release and make sex hormones

Ovaries

• Location: Lower abdomen/groin

• Function: Release and make sex hormones that control menstrual cycle and pregnancy