BIO 2870 Chapter 8

What 2 organ systems coordinate all activities that maintain homeostasis?

What 2 organ systems coordinate all activities that maintain homeostasis?

Nervous and endocrine

This organ system's responses are fast and brief

Nervous system

This organ system's responses are slower and longer

Endocrine system

The 3 main functions of the nervous system are:

1. Monitors the body's internal and external environments

2. Integrate sensory information

3. Coordinate voluntary and involuntary responses

This division includes the brain and spinal cord; it integrates and coordinates sensory processing and motor transmission; it is the locations of higher functions

Central nervous system

This division is all the nervous tissue outside the CNS; it is the communication connection between the CNS and the rest of the body

Peripheral nervous system

This division of the PNS brings info. to the CNS from receptors in body tissues and organs

Afferent

This division of the PNS carries information away from the CNS to effectors (muscles and glands that respond to motor commands)

Efferent

This division of efferent controls skeletal muscle contractions

Somatic nervous system

This division of efferent controls smooth and cardiac muscles and glands

Autonomic nervous system

What are the 3 parts of the ANS?

Sympathetic (increases heart rate), parasympathetic (decreases heart rate), and enteric (helps control digestive functions independent of the CNS)

Nervous tissue is made of

Neurons and neuroglia

Unlike neurons, neuroglia are able to

Divide

This carries signals away from the cell body

Axon

These receive signals coming into the body

Dendrites

In the cytoplasm of the neuron cell body, free ribosomes and RER form _______________, giving gray color to areas with many cell bodies

Nissl bodies

This is the thickened region marking the beginning of the axon, originating point for electrical impulses (action potentials)

Axon hillock

Most neurons lack ______________ so they cannot divide or be replaced

Centrioles

Neural stem cells are typically inactive, except for those found in nose and

Hippocampus

This is the most common neuron in the CNS, it has 2+ dendrites and 1 axon, and it includes all motor neurons controlling skeletal muscles

Multipolar neuron

This kind of neuron has a single elongated process with the cell body off to the side; most common neuron in the PNS

Unipolar

This kind of neuron has one dendrite and one axon and is rare

Bipolar

These neurons receive info from sensory receptors and relay that info to the CNS

Sensory or afferent neurons

These neurons carry instructions away from the CNS; peripheral targets of these instructions are called effectors

Motor or efferent neurons

These neurons are located entirely in the CNS and interconnect other neurons

Interneurons

What are the two types of somatic sensory receptors?

External receptors: Monitor the external environment Proprioceptors: Monitor position and movement of skeletal muscles and joints

This kind of sensory neuron monitor activities of internal organs and provide sensations of distention, deep pressure, and pain

Visceral/internal receptors

These innervate skeletal muscles

Somatic motor neurons

These innervate cardiac muscle, smooth muscle, and glands

Visceral motor neurons

These function as links between sensory and motor neurons; they play a role in all higher functions (memory, planning, learning)

Interneurons

Astrocytes, oligodendrocytes, microglia, ependymal cells are what kind of cells found where?

Neuroglia; found in the CNS

These are star-shaped cells; the most numerous neuroglia; maintain the blood-brain barrier and isolates CNS from general circulation

Astrocytes

These cells produce an insulating membranous wrapping around axons called myelin, which acts as electrical insulation and increases the speed at which action potential travels along the axon

Oligodendrocytes

Areas of axons covered in myelin are called___________. Small gaps between are called _______________, where there is no myelin.

Internodes; nodes of Ranvier

White matter of the CNS is dominated by

Myelinated axons

Gray matter of the CNS consists of

Neuron cells bodies, dendrites, and unmyelinated axons

These are the smallest and least numerous neuroglia in CNS; they are phagocytic cells derived from white blood cells

Microglia

These neuroglia line the cavities of the CNS filled with cerebrospinal fluid; its cells are involved in producing and circulating cerebrospinal fluid within and around CNS

Ependymal cells

The two types of neuroglial cells in the PNS include:

Satellite cells and schwann cells

These neuroglial cells of the PNS surround and support neuron cell bodies; they're similar in function to astrocytes in CNS

Satellite cells

These neuroglial cells of the PNS cover every axon in the PNS; they produce myelin

Schwann cells (neurolemmocytes)

Outer surface of schwann cell is called

Neurolemma

Myelinated axons have one ____________ per segment

Schwann cell

One schwann cell can encircle many ____________________

Unmyelinated axons

The destruction of myelin sheaths in both CNS and PNS; results in loss of sensation and motor control

Demyelination

This disease affects axons in the brain, optic nerves, and/or spinal cord

Multiple sclerosis

Heavy metal poisoning by mercury or lead and bacterial diseases such as diptheria are examples of

Demyelination disorders

(PNS) Collection of neuron cell bodies are located in

Ganglia

(PNS) Bundles of axons are called

Nerves

(PNS) Spinal nerves are connected to the _______________. Cranial nerves are connected to the ______________.

Spinal cord; brain

(CNS) Collections of neuron cell bodies are located in

Centers or nuclei

(CNS) Bundles of axons are called ___________. In the spinal cord, form larger groups called _______________.

Tracts; columns

Sensory, or ascending, pathways carry information to the

CNS

Motor, or descending, pathways carry information away from the

CNS

All living cells have a polarized plasma membrane, which means

Excessive positive charge outside the cell and excessive negative charge inside the cell

The potential difference between the two charges inside and outside the cell is called

Membrane potential or transmembrane potential

Membrane potential of undisturbed cell is called_______________ and the resting membrane potential of neurons is _______.

Resting membrane potential; -70 mv

Leak channels are always ___________. Na+ and K+ are leak channels.

Open

These channels open or close under specific circumstances

Gated

Channels and carriers mediate passive transport, while carriers (transporters) also mediate ________________. They are called _______________.

Active transport; Pumps

Chemically-gated ion channels open or close in response to the binding of a specific _________________________. An example is

Chemical messenger; acetylcholine receptor

Voltage-gated ion channels open or close in response to the changes in

Membrane potential

Na+ moves into the cell and K+ moves out of the cell by

Passive transport; more Na+ outside the cell than inside and more K+ inside the cell than outside

In the sodium-potassium pump, how many Na+ move out and how many K+ move in?

3 Na+ out for every 2 K+ in

Opening gated Na+ channels speeds up entry of Na+, which shifts the membrane potential in a positive direction (towards 0 mV). This is called

Depolarization

Opening gated K+ channels allows more K+ to leave, shifting the membrane potential in a negative direction to -80 mV. This is called

Hyperpolarization

Changes in the membrane potential that cannot spread far from site of stimulation; degree of depolarization decreases with distance from stimulus site; occurs in plasma membrane of all cells; can only trigger activation of large neurons and skeletal muscle fibers if lead to production of an action potential

Graded or local potentials

Propagated change in membrane potential of excitable cells; change in membrane potential travels the entire length of cell and doesn't diminish as it moves away from source

Action potential, or nerve impulse in a neuron

The level of depolarization required to initiate an action potential

Threshold

Every stimulus that brings membrane to threshold will result in an identical action potential; action potential will propagate down the length of the neuron

All-or-none principle

Time from voltage-gated sodium channels opening until repolarization is complete; membrane cannot respond to further stimulation; limits rate of response by neurons

Refractory period

Site where neuron communicates with another cell

Synapse

In the synapse, information is transferred through release of chemical messengers called _____________, where communication happens in one direction only.

Neurotransmitters

Synapse between a neuron and another cell type is called a

Neuroeffector junction

Synapse between a neuron and muscle cell is called a

Neuromuscular junction

Synapse between a neuron and a secretory cell is called a

Neuroglandular junction

Neuron on sending side of synapse; neurotransmitters are released and diffuse across synaptic cleft

Presynaptic neuron

Neuron on receiving side of synapse; has receptors for neurotransmitters

Postsynaptic neuron

Acetylcholine (ACh) is released at

Cholinergic synapse

ACh is removed by

Acetylcholinesterase (AChE)

Common neurotransmitter important in the brain and part of the ANS; released by adrenergic synapses

Norepinephrine (NE)

These function as CNS neurotransmitters

Dopamine, GABA, and serotonin

These are gases that act as neurotransmitters

Nitric oxide (NO) and carbon monoxide (CO)

ACh and NE trigger

Depolarization (excitatory)

Dopamine, GABA, and serotonin trigger

Hyperpolarization (inhibitory)

Group of interconnected interneurons with specific functions are called

Neural pools

One presynaptic neuron with several postsynaptic neurons

Divergence

Several presynaptic neurons with single postsynaptic neuron

Convergence

The meninges are 3 layers of specialized membranes; they provide physical stability and shock absorption; cranial meninges and spinal meninges

Pia mater, arachnoid, and dura mater

The dura mater is the tough, fibrous outer layer with two layers. The outer layer is fused to the periosteum of the skull and these hold the brain in position

Dural folds

The dura mater has large collecting veins called

Dural sinuses

The spinal cord dura mater is separated from the vertebrae by the

Epidural space

Layer of squamous epithelial cells separated from dura mater by subdural space

Arachnoid

Deep to arachnoid, created by web of collagen and elastic fibers, filled with cerebrospinal fluid

Subarachnoid space

Acts as shock absorber and transports dissolved gases, nutrients, chemical messengers, and waste products

Cerebrospinal fluid (CSF)

Innermost meningeal later, highly vascularized (provides needed oxygen and nutrients to superficial areas of neural cortex)

Pia mater

Major neural pathway between brain and PNS; controls spinal reflexes

Spinal cord

These two areas of the spinal cord are enlarged

Cervical enlargement and lumbosacral enlargement

This narrow internal passageway of the spinal cord is filled with CSF

Central canal

Spinal ganglia and dorsal root ganglia contain

Cell bodies of sensory neurons