Nervous System Chapter 12

Nervous systems major function: Process and coordinate sensory data inside and outside the body, controls activities of peripheral organs, intelligence, memory, learning, and emotion. Delivers sensory information to the CNS. Carries motor commands to peripheral tissues and systems.

Central nervous system (CNS): CNS includes spinal cord and brain along with neural tissue, connective tissue, and blood vessels.

Functions of CNS: Process and coordinate: -Sensory data: from inside and outside the body -Motor commands: controls activities of peripheral organs (ex: skeletal muscles) -Higher functions of brain: intelligence, memory, learning, emotion

Action potential: A propagated change in the transmembrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions.

Peripheral nervous system (PNS): Neural tissue outside the CNS Functions of PNS: Deliver sensory information to the CNS. Carry motor commands to peripheral tissues and systems.

Somatic nervous system (SNS): Controls skeletal muscle contractions voluntary or involuntary (reflexes) muscle contractions Autonomic nervous system: Controls subconscious actions: contractions of smooth muscle and cardiac muscle and glandular secretions -Sympathetic division: stimulating effect (raising the heart rate) -Parasympathetic division: relaxing effect (slowing the heart rate)

Afferent neurons: Sensory nerves. Monitor internal environment and effects of external environment. brings sensory information to the CNS from receptors in peripheral tissues and organs.
Efferent neurons: Motor neurons. Carry instructions for CNS to peripheral effectors via efferent fibers. carries motor commands from the CNS to muscles, glands, and adipose tissue. Target organs that respond by doing something are called effectors.

Neurons: Basic functional units of the nervous system. Send and receive signals called action potentials.
Neuroglia: Supporting cells that separate and protect neurons, provide a supportive framework for neural tissue, act as phagocytes, and help regulate the composition of interstitial fluid

In CNS large cell bodies with many processes. Maintain BBB, create 3-D framework for CNS, repairs damaged neural tissue, guides neuron development, and control interstitial environment

In CNS smaller cell bodies with fewer processes. Processes contact with other neuron cell bodies. Wrap around axons to form myelin sheats

In CNS smallest and least numerous neuroglia with many fine-branched processes. Microglia are the phagocytes of CNS. Migrate through neural tissue. Clean up after cellular debris, waste products, and pathogens. Police and janitor of CNS

Ependymal cells: In CNS cells with highly branched processes, contact neuroglia directly. Form epithelium called ependyma. Line the central canal of spinal cord and ventricles of the brain -Secret cerebrospinal fluid (CSF) -Have cilia or microvili that circulate CSF -Monitor CSF -Contain stem cells for repair

AKA neurilemmocytes. Form myelin sheath around peripheral axons. One Schwann cell sheaths one segment of axon. Many Schwann cells sheath entire axon.

AKA amphicytes. Surround ganglia (masses of neuron cell bodies found in PNS surrounded by neuroglia). Regulate environment around neuron

Cell body: (soma) contains a relatively large round nucleus with a prominent nucleolus Perikaryon: Cytoplasm surrounding nucleus Nissl bodies: Dense areas of RER and ribosomes. Make neural tissue appear gray (gray matter) Neurofibrils: BUdndles of nuerofilaments that provide support for dendrites and axon Dendrites: Highly branched. Dendritic spine has many fine processes and receive information from other neurons. 80-90% of neuron surface areas Axon: Long and carries electrical signal (action potential) to target. Axon structure is critical to function of neuron

•Occasional branches (axon collaterals) Axons bifurcate and can send a branch back toward its own cell's soma.
•Branches profusely at end (terminus) Can be 10,000 terminal branches (also called telodendria
•Distal endings called axon terminals or terminal boutons