Chapter 12 Neurons & Nervous Tissue

Sections of the Nervous System

Central

Peripheral

Central Nervous System comprises of

brain & spinal cord

Peripheral Nervous System comprises of

nervous tissue outside CNS and ENS

Two Kinds of Cells in Nervous System

neurons

neuroglia (suppporting cells)

Types of Tissues Found in Nervous System

Special Sensory Receptors

monitor smell, taste, vision, balance, and hearing

Visceral Sensory Receptors

monitors internal organs

Somatic Sensory Receptors

monitor skeletal muscles, joints, and skin

• movement, temp, pain, pressure, vibration

Afferent Division

part of PNS that is responsible for transmitting sensory information from the body's sensory receptors to the CNS

Effectors

structures that respond to incoming neural signals

Receptors

structures that detect changes

Information Processing in the CNS

integrates, processes, and coordinates sensory input and motor commands

Efferent Division

part of the PNS that is responsible for carrying signals from the CNS to the body

Somatic Nervous System (SNS)

controls voluntary functions such as muscle movement

Autonomic Nervous System (ANS)

controls involuntary functions such as heart rate and digestion

automatically regulates smooth muscle, cardiac muscle, gladular secretions, adipose tissue

Parasympathetic Division

controls the body during rest and digestion

Sympathetic Division

controls the body during times of stress

aka “fight or flight”

Regions of the Neuron

Axon

Cell Body

• Perikaryon

• Nucleus

Dendrites

Telodendria / Axon Terminal

Nissl Bodies

region of the cell body where RER and free ribosomes are located

only found in neurons

reason for gray matter

Anterograde Transports

from soma to terminals

Retrograde Transport

from terminals to soma

Synaptic Vesicle

store neurotransmitters that is moved via a kinesin protein in the axon

Structural Classes of Neurons

Anaxonic

Bipolar

Unipolar

Multipolar

Anaxonic Neuron

have more than 2 processes and they may all be dendrites

Bipolar Neuron

have 2 processes separated by the cell body

Unipolar Neurons

have single elongated process with cell body located off to the side of its axon

most common type of sensory neuron in PNS

Multipolar Neuron

have more than 2 processes with a single axon and multiple dendrites

characteristic of all motor neurons

Functional Classes of Neurons

Sensory Neuron

Motor Neuron

Interneuron

Types of Sensory Neurons

Somatic Sensory Neurons

• external environment

Visceral Sensory Neurons

• internal environment

Sensory Receptors

Interal Systems (i.e. digestive, etc.)

Internal Senses (stretch, pain)

Somatic Senses (temp, pain, etc.)

Proprioceptors (position, movement of muscles & joints)

where do Motor (Efferent) Neurons send signals

Somatic MNs

• skeletal muscle

Visceral MNs (ANS)

• smooth, cardiac muscles, glands, adipose tissue

what chemical do MN Neurotransmitters sent to somatic MN

Achetylcholine

what chemical do MN Neurotransmitters sent to visceral MN

Acetylecholine (parasympathetic)

Norepinepherine (sympathetic)

MN Target Organ Receptors for Skeletal Muscles

nicotonic acetylcholine receptors

MN Target Organ Receptors for Smooth & Cardial Muscle, Glands, Adipose Tissue

Muscarinic AChRs

Adrenergic Receptors

Primary Location of Interneurons

brain & spinal cord

Purpose of Interneurons

distribute sensory info

cooridnate motor activity

involved in high functions (i.e., memory, planning)

Types of Neuroglia of CNS

astrocytes

ependymal cells

oligodentries

microglia

Astrocytes

• anchor nuerons to capillaries for material exchange

• maintain BBB

• provide strucutral support

• regulate ion, nutrient, dissolved gas conc

• absorb & recyle neutrotransmitters

• form scar tissue after injury

Ependymal Cells

• simple cuboidal epithelial cells that line brain and spinal cord

• produce, circulate, monitor cerebrospinal fluid (CSF)

Oligodendrocytes

• cells with sheet-like processes that wrap around axons

• help form myelin sheath

• provide structural framework

Microglia

• remove cell debris, waste, pathogens by phagocytosis

Purpose of Myelin Sheath

• provides protective insulation

• affects how fast signals travel through those nerve cells

• maintains the strength of the impulse message as it travels down the axon

Types of Neurglia of PNS

Satellite Cells

Schwann Cells (Neurolemmocytes)

Satellite Cells

• surround clusters of neuronal cell bodies or ganglia

  • regulates fluids around ganglionic neurons

Schwaan Cells

• wrap plasma membrane around axons

• outer surface called neurolemma

• each cell forms an individual myelinated internode

Rabies is a viral disease contracted from the bite of an infected animal. Rabies bypasses many immune system defenses by traveling in peripheral neurons to reach the CNS. Which methods of transport are used by the rabies virus to reach the CNS?

Axoplasmic Transport

• virus particles can travel w other materials along molecular motors in cytoplasm

• specifically Retrograde Flow (type of axoplamic)

  • substance flow from axon to cellbody and destroys neuron

Osmosis

• viruses can dlow in & among cells by traveling along water routes