Nervous system

A. Four Major Functions Receive input from internal and external environments Transmit information between nerve cells and brain.

3. Process information

4. Respond to stimuli

How it Works A. Receptors (sensory nerves)sense changes in the internal or external environments. B. Effectors (motor nerves)carry out the desired response.

Sensory input can be in many forms Mechanoreceptors – sound, pressure, touch, Chemoreceptors – taste, smell Photoreceptors- light Thermoreceptors - Temperature

C. The input is converted to a signal and sent to the brain or spinal cord

Two main parts of nervous system 1. Central Nervous System (CNS)- includes the brain and spinal cord.

2. Peripheral Nervous System (PNS)- connects the CNS to other parts of the body, and is composed of nerves (bundles of neurons).

Two types of cells Neurons and Neuroglial Cells 1. Neurons Functional unit of the nervous system

neuron

B. Supporting cells (neuroglial) cells protect, support and assist the neurons 1. Schwann cells- found in PNS wrap around nerve fibers contain myelin- help transmit signals faster 2. Astrocytes-supply neurons with O2 and nutrients in CNS 3. Microglial- support neurons in CNS 4. Oligodendrocytes- Myelin sheaths in CNS 5. Ependymal cells- forms special ephithelial tissue around different parts of the brain, ventricles and spinal cord

Schwann cells- found in PNS wrap around nerve fibers contain myelin- help transmit signals faster

Astrocytes-supply neurons with O2 and nutrients in CNS

Microglial- support neurons in CNS Support neurons and phagocytize bacterial cells and cellular debris.

E. Structure of Neurons Cell body (Soma) Axon Dendrites Nucleus Synaptic knob Myelin Nodes of ranvier

F. Types of Neurons Sensory- Receive and carry information to CNS from internal and external enviro. Interneurons- found in CNS carry impulses from one area to another Motor-Carry impulses from CNS to effectors.

Nerve Pathways 1. Reflex arc- sensory neuron, to interneuron, to motor neuron

reflex arcs include balance, blinking and knee-jerk.

2. Reflex- automatic subconscious response to a stimuli. 3. knee-jerk reflex- patellar ligament Quadriceps femoris contracts Helps maintain balance

4. Withdrawal reflex- response to painful stimuli body part is subconsciously quickly removed from the stimulus

Conducts nerve impulses throughout the body. -impulses are created by a difference in electrical and chemical charges between one side of the cell membrane and the other.

3. Neurotransmitters- send chemical signals from one neuron to another across a synapses 4. Synapses- gap between neurons http://www.brainpop.com/health/nervoussystem/nervoussystem/

A. CNS (central nervous system) 1. Spinal Cord: A.) Located inside the spine

B) Relays nerve impulses to & from the brain C) controls spinal reflexes such as the reflex arc i. The reflex arc is an automatic, involuntary reaction to a stimulus.

B. PNS (Peripheral Nervous System) A. Two main components of the PNS: 1.) Sensory (afferent) pathways- - provides input from body (internal and external information) to CNS.

2) Motor (efferent) pathways that carry signals to muscles and glands (effectors) from CNS. -Autonomic -Somatic

Peripheral nervous system PNS Sensory division Motor division autonomicANS involuntary Sensing external environment Sensing internal environment Somatic SNS voluntary Parasympathetic division Sympathetic division

I. The Somatic Nervous system (SNS) 1. That part of the PNS that includes all nerves controlling the muscular system and external sensory receptors.

II.Autonomic nervous system motor neurons that control internal organs. muscles in the heart, smooth muscle in internal organs such as the intestine, bladder, and uterus. Sympathetic Parasympathetic

a. Sympathetic branch of the ANS sympathetic branch Autonomic NS prepares the body for emergencies: "fight or flight". Stimulated by epinepherine

b. Parasympathetic branch of the ANS Returns body functions to normal after they have been altered by sympathetic stimulation. Stimulated by Norepinepherine

2. Brain (5 Major Regions) A) Brain stem- Coordinates functions such as breathing, heart rate, & sleep Contains: midbrain, pons, and medulla oblongata

i. Midbrain- ii. Pons- iii.Medulla Oblongata- controls visceral activities: cardiac, vasomotor, and respiratory center

B. Diencephalon 1. Thalamus directs messages from spinal cord to correct parts of the brain Senses Pain

C. Hypothalamus Monitors the homeostasis (hunger, thirst, temp., ect.) Link between nervous & endocrine systems

D. Cerebellum Coordinates muscle activities, balance, equilibrium & posture

E. Cerebrum Voluntary (conscious) activity Sensory Speech, language, memory