Chapter 8 Nervous System 5 Functions 1. Sensory function = receptors monitor external & internal body changes; providing input 5 Functions 1. Sensory function = receptors monitor external & internal body changes; providing input

Functions continued: 2.Integration function = brain & spinal cord process sensory information from receptors & initiate a proper response

Functions continued: 3. Motor function = output response from brain & spinal cord by way of nerve impulses to effectors (muscles, glands, etc)

Functions continued Homeostasis-Depends on the ability of the NS to detect, interpret, and respond to change in internal and external conditions. In response, the NS can stimulate or inhibit the activities of other systems to maintain homeostasis. 4. Homeostasis-Depends on the ability of the NS to detect, interpret, and respond to change in internal and external conditions. In response, the NS can stimulate or inhibit the activities of other systems to maintain homeostasis.

Functions continued 5. Mental Activity-The brain is the center of mental activity, including consciousness, memory, and thinking.

Organization

-2 Major Division 1. CNS (central nervous system) = brain, spinal cord, nuclei -2 Major Division 1. CNS (central nervous system) = brain, spinal cord, nuclei

Organization -2 Major Division 2. PNS (peripheral nervous system) = nerves (cranial & spinal nerves) & ganglia

Organization: Divisions of PNS PNS (peripheral nervous system) is further divided into 2 divisions: 1. Sensory division = nerves which send impulses to CNS from receptors

Organization: Divisions of PNS PNS 2. Motor Division = nerves which carry impulses away from CNS to effectors (muscles, glands)

Organization: Divisions of PNS PNS Motor Division is further divided into 1. Somatic Nervous System = (SNS) nerves that carry impulses away from CNS to voluntary effectors (skeletal muscles)

Organization: Divisions of PNS PNS Motor Division is further divided intoPNS Motor Division is further divided into 2. Autonomic Nervous System (ANS) = nerves which carry impulses away from CNS to involuntary effectors (glands, heart, smooth muscle)

Organization: Divisions of PNS PNS Motor Division, Autonomic Nervous System (ANS) is further divided into - PNS Motor Division, Autonomic Nervous System (ANS) is further divided into 1. Parasympathetic Division = carries impulses away from CNS to involuntary effectors under normal conditions

Organization: Divisions of PNS 2. Sympathetic Division = carries impulses away from CNS to involuntary effectors under stressful conditions - Sometimes called “fight or flight”

Autonomic Nervous System Can be divided into: –Sympathetic Nervous System “Fight or Flight” –Parasympathetic Nervous System “Rest and Digest” These 2 systems are antagonistic. Typically, the 2 divisions are balanced to keep the body in a state of dynamic balance.

ANS: ANS: -Sympathetic & Parasympathetic tend to produce opposite results on their effectors

SympatheticParasympathetic  heart rate  heart rate  resp. rate  resp. rate  sweating None

SympatheticParasympathetic Pupil dilationPupil constriction  Digestion  Digestion blood vessel dilation in skeletal muscles None

SympatheticParasympathetic Blood vessel constriction in skin & viscera None  Adrenal hormones (adrenalin or epinephrine) None

Nervous Tissue (primary cells) Primary cells: Neurons/Neuroglia 1. Neurons = produce & conduct nerve impulses (electrical events): - Major cells parts a. cell body = contains main organelles (nissl bodies = rough E.R.)

Major cells parts b. 2 cell processes = cell extensions from the cell body - dendrites = carry impulse to cell body, may be branched - axon – carries impulse away from cell body

c. Axon terminal = swollen ending of axons contain synaptic vesicles with chemicals (neurotransmitters)

Direction of Impulse: dendrite cell axon body body

d. axon hillock = expanded portion where the axon joins the cell body joins the cell body

e. myelin sheath = whitish insulation layer surrounding axon, protects & increases axon, protects & increases speed of nerve impulses speed of nerve impulses -actually formed by Schwann cells (a neuroglial cell) cells (a neuroglial cell)

2 types neurons 2 types neurons - myelinated neurons - myelinated neurons (white matter) - unmyelinated neurons - unmyelinated neurons (gray matter)

f. Neurilemmal sheath = surrounds myelin sheath, used in repair of axon used in repair of axon

g. Nodes of Ranvier = small areas on myleinated axon where no myelin sheath is where no myelin sheath is formed. formed.

By definiton: By definiton: 1. clusters of cell bodies in the CNS (brain & spinal cord) CNS (brain & spinal cord) Nuclei in the CNS

By Function : By Function : (what they do?) 1. sensory neuron = carries impulses to CNS 2. motor neuron = carries impulses away from the CNS to effectors (what they do?) 1. sensory neuron = carries impulses to CNS 2. motor neuron = carries impulses away from the CNS to effectors Types of Neurons

3. interneuron = neurons between sensory & motor neurons; located only in neurons; located only in CNS CNS Types of Neurons

By structure By structure (what they look like?) 1. multipolar neuron = one axon & many highly branched dendrites Types of Neurons

2. bipolar = one axon & one dendrite on opposite sides of cell body

3. unipolar neuron = one axon & one dendrite connected to & one dendrite connected to cell body by a small cell body by a small T-like process (ie one process T-like process (ie one process extends from the cell body) extends from the cell body)

multipolar neurons = motor neuron & interneurons bipolar neurons = sensory neurons, usually in eye unipolar neurons = sensory neurons in skin

Nervous Tissue (2 primary cell types) 2. Neuroglia = 5 types of supportive cells: -Oligodendrocytes, Schwann cells. Microglia, astrocytes, ependymal 2. Neuroglia = 5 types of supportive cells: -Oligodendrocytes, Schwann cells. Microglia, astrocytes, ependymal

46 Types of Neuroglia Oligodendrocytes: produce myelin sheath in CNS Microglia: help remove bacteria and cell debris from CNS

47 Types of Neuroglia Astrocytes: - star-shaped - most abundant - form blood-brain barrier Ependymal Cells: produce and circulate cerebrospinal fluid (CSF)

48 Types of Neuroglia Schwann cells: produce myelin sheath around around axons in PNS

Saltatory conduction in a myelinated axon

51 Synapse What is it? - where an axon comes in close contact to a muscle, gland, organ, or other neuron - involved with release of neurotransmitters - Ex. Neuromuscular junction

Figure 8.13

Neuronal Pathways Converging: - two or more neurons synapse on same neuron - allows info. to be transmitted in more than one neuronal pathway to converge into a single pathway Diverging: - axon from one neuron divides and synapses with more than one neuron - allows info. to be transmitted in one neuronal pathway to diverge into 2 or more pathways 54