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:
Monitors the body's internal and external environments
Integrate sensory information
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