Nervous System

By: Joe MattenCasey Crocamo

Kevin LiAllie Erickson

Wenyi Lau

Nervous System

• Neurons can help to take in stimuli from both outside and inside the body.

• They can process these stimuli to control other bodily functions.(motor output)

• The three types of neurons are sensory(afferent), interneurons, and motor(efferent)

• A good way to remember the difference is efferent=effect

Nervous System(CNS+PNS)

• The nervous system is separated into two parts, peripheral and central.

• The central includes the brain and the spinal cord.

• The peripheral includes all of the nerves outside of the brain and spinal cord

PNS

• PNS is separated into the somatic (voluntary) and autonomic (involuntary) systems.

Types of nervous system cells

• Astrocytes, microglia, ependymal, oligodendrocytes, satellite, schwann.

• Astrocytes are starshaped, they form the barrier between the capillaries and neurons in the brain.

• Microglia are spider-like phagocytes that collect trash.

• Ependymal cells line the brain+spinal cord spaces. They help move CSF.

Nervous system cells

• Oligodendrocytes produce myelin sheath around nerve fibers in the CNS

• Satellite cells protect neurons• Schwann cells produce myelin sheath around

the nerve fibers in the PNS

Cell Body

• Nissl substance is the specialized rough ER• Neurofibrils provide a cytoskeleton that helps

cells maintain their shape

Neurons

• Dendrites conduct impulses towards the body, while Axons take them away from the body.

• There are axon terminals with vesicles and neurotransmitters. They are separated with a synaptic cleft.

• Schwann cells produce myelin sheaths. The gaps between these schwann cells are called the Nodes of Ranvier.

Cell bodies

• Gray matter consists of cell bodies and unmylenated fibers.

• Nuclei are clusters of cell bodies within the white matter.

Cell bodies

• Multipolar neurons have multiple extensions from the body

• Bipolar neurons have one axon and one dendrite

• Unipolar neurons have a short single process leaving the cell body.

Neurons

• The plasma membrane is polarized at -70mv• There are more sodium ions outside of the

membrane, with more potassium ions inside the membrane.

• Threshold is at -55mv.• It depolarizes, Na+ channels open to let sodium

ions flow in. • It then repolarizes, the potassium channels

opens and the potassium ions are sent in.

Neurons

• It then hyperpolarizes for a few milliseconds and enters the refractory period where it cannot transmit any signals

Reflex Arc

• The reflex arc is the route from a sensory neuron to an interneuron then to an effector.

• There are two types of reflex arcs, autonomic and somatic.

• Autonomic reflexes include smooth muscle regulation, heart+blood pressure regulations, glandular regulation and digestive system regulations.

• The somatic reflexes include activation of skeletal muscles

CNS

• The CNS develops from the embryonic neural tube, includes the brain and the spinal cord. There are four chambers in the brain filled with CSF.

• There are 4 main regions of the brain, the cerebral hemispheres, diencephalon, brain stem and cerebellum.

• There cerebrum has a frontal, parietal, occipital and temporal lobe.

Lobes of The Brain

• Frontal Lobe• Parietal Lobe• Occipital Lobe• Temporal Lobe

Cerebrum

• The cerebrum consists of an outer layer made up of gray matter.

• The cerebral cortex is involved in speech, memory, logical and emotional responses, consciousness, interpretation of sensation, and voluntary movement

White Matter

• Corpus Callosum connects the hemispheres of the brain.

Diencephalon

• Made of three parts:• Thalamus• Hypothalamus• Epithalamus

Diencephalon

• Thalamus: relays sensory impulses• Hypothalamus: helps to regulate body

temperature, controls water balance and regulates metabolism

• Part of limbic system • Epithalamus: includes pineal gland and the

choroid plexus (forms CSF)•

Brain Stem

• Midbrain: reflex centers for vision and hearing • Pons: control of breathing • Medulla oblongata: heart rate control, blood

pressure regulation, breathing, swallowing and vomiting

Reticular Formation

• Involved in sleep/wake cycles and consciousness

• Also involved in motor control of visceral organs

Cerebellum

• coordination of body movements

• The central nervous system is protected by the scalp, skin, skull, cerebrospinal fluid, blood brain barrier and vertebral column and the meninges

Meninges

• Dura mater: exterior cover and contains periosoteum and meningeal layer

• Arachnoid layer: middle layer and is web-like• Pia mater: the internal layer and clings to the

surface of the brain

Cerebrospinal Fluid

• Formed by the choroid plexus and protects and cushions the brain

• Found inside the arachnoid space

Blood Brain Barrier

• Protects the brain from harmful substances• The things that can pass through:• Fats and fat soluble molecules • Respiratory gases• Alcohol• Nicotine• Anesthesia

Traumatic Brain Injuries

• Concussion: slight brain injury and leads to no permanent brain damage

• Contusion • Nervous tissue destruction occurs • Nervous tissue does not regenerate • Cerebral edema • Swelling from the inflammatory response • May compress and kill brain tissue ; 3 ;

Stroke

• Cerebrovascular Accident (CVA)• Caused by a ruptured blood vessel and results

in oxygen deprivation

Alzheimer’s disease

• This is when victims experience memory loss, irritability, confusion, and hallucinations and eventually death

Spinal Cord

• Carries nerve impulses from the brain to the limb

• Protected and cushioned by the meninges

Peripheral Nervous System

Structure of a Nerve

• Outer: endoneurium• Middle: perineurium • Inner: epineurium