chapter 37 pp Flashcards
The Central Nervous System
Consists of the brain and spinal cord
Hydras
Nerve net composed of neurons in contact with one another
Also in contact with contractile cells in the body wall
RELY ON THE FLOW OF WATER
Planarians
Ladderlike nervocus system
Two ventrally located bundles of nerves extending from the cerebral ganglia to their posterior end
Cephalization – a concentration of ganglia and sensory receptors in the head (anterior region)
Bilateral symmetry and cephalization are two significant adaptive trends in nervous system development.
Annelids and Arthropods
Complex animals
Typical invertebrate nervous systems
A brain is present and a ventral nerve cord has a ganglion in each segment.
Molluscs
what is a mollusk? Snails oysters squids
Cephalopods have a well-defined brain and sense organs.
Vertebrate brain is organized into three areas
hind brain, mid brain, forebrain
Hindbrain
Regulates motor activity below level of consciousness
Medulla oblongata contains control centers for the heart and breathing
Midbrain
The optic lobes are part of the midbrain.
Originally was a center for coordinating reflexes involving eyes and ears.
Forebrain
In early vertebrate evolution, forebrain was concerned mainly with sense of smell.
In the forebrain, the hypothalamus is concerned with homeostasis and communicates with the medulla oblongata and pituitary gland.
The hindbrain and midbrain of mammals are similar to those of
vertbrates
The forebrain of mammals
is greatly enlarged
neocortex
outer layer, only seen in mammals
Forebrain in mammals functions for higher mental process
Spatial reasoning
Conscious thought
Language
Frontal lobes in mammals
are large and complex in primates
Increased brain capacity allowed mammals, especially humans, to become adept at higher mental activities.
This provided tremendous evolutionary advantages.
how is the nervous system separated?
in the central nervous system and Includes the brain and the peripheral nervous system.
The peripheral nervous system (PNS)
Consists of all nerves and ganglia that lie outside the CNS
Two divisions
Somatic nervous system
Sensory and motor functions that control skeletal muscle
Autonomic nervous system
Controls smooth muscle, cardiac, muscle, and glands
Divided into sympathetic and parasympathetic divisions
The central nervous system (CNS)
Includes the brain and spinal cord
meninges
wha thte Spinal cord and brain are wrapped in three protective membranes
cerebrosphal fluid
this is what fills the spaces
ventricles
Fluid is continuous with that of central canal of spinal cord and the ventricles of the brain
Meningitis
is a serious disorder caused by bacteria or viruses that invade the meninges.
The Spinal Cord
Two main functions
Center for many reflex actions
Automatic responses to external stimuli
Means of communication between the brain and spinal nerves
Composed of grey matter and white matter
Cell bodies and short unmyelinated fibers give the gray matter its color.
Myelinated long fibers of interneurons running in tracts give white matter its color.
White matter tracts connect spinal cord to brain
Cerebral Cortex
A thin but highly convoluted outer layer of gray matter
Covers the cerebral hemispheres
Contains motor areas and sensory areas as well as association areas
Primary motor area
is in the frontal lobe, just ventral to the central sulcus.
Primary somatosensory area
is in the parietal lobe, just dorsal to the central sulcus.
Basal nuclei
Integrate motor commands
Ensures that the proper muscle groups are either activated or inhibited
Parkenson’s disease
Basal Nuclei
is a brain disorder characterized by tremors, speech, and difficulty standing and walking.
Results from loss of dopamine-producing cells in the basal nuclei
Diencephalon Region
A region encircling the third ventricle
Includes three structures:Hypothalamus, Thalamus, Pineal gland
Hypothalamus
Forms the floor of the third ventricle
Integrating center that maintains homeostasis
Controls the pituitary gland
Thalamus
Consists of two masses of gray matter located in the sides and roof of the third ventricle
Receives all sensory input except smell
Integrates sensory information and sends it to the cerebrum
Pineal gland
Secretes melatonin
Hormone involved in maintaining normal sleep-wake cycle
Cerebellum
Separated from the brain stem by the fourth ventricle
Largest portion of the brainstem
Receives sensory input from the eyes, ears, joints, and muscles
Sends motor impulses out the brain stem to the skeletal muscles
Brainstem
Contains the midbrain, pons, and the medulla oblongata
Midbrain
Acts as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum
Pons
Pons
Contains axons that form a bridge between the cerebellum and the rest of the central nervous system
Medulla Oblongata
Contains reflex centers for vomiting, coughing, sneezing, hiccupping, and swallowing
The Reticular Activating System (RAS)
A complex network of:
Nuclei (masses of gray matter)
Nerve fibers that extend the length of the brain stem
The reticular formation is a major component of the RAS.
The RAS arouses the cerebrum via the thalamus and causes a person to be alert.
Limbic System
Complex network of tracts and “nuclei”
Incorporates
Medial portions of the cerebral lobes,
The basal nuclei, and
The diencephalon
Integrates higher mental functions and primitive emotions
Important structures in the limbic system are
Memory
The ability to hold a thought in mind or recall events from the past
Learning
Takes place when we retain and use past memories
Short-term memory is associated with
the prefrontal area of the frontal lobe.
Long-term memory is associated with
the hippocampus.
Gathers long-term memories stored in sensory association areas
Makes them available to the frontal lobe
somatic system
vountary
Includes paired cranial nerves and spinal nerves
Gather information from sensors and conduct decisions to effectors
Controls the skeletal muscles
autonomic system
(usually involuntary)
Controls the smooth muscles, cardiac muscles, and glands
Innervates all internal organs
Divided into two divisions
Sympathetic division
Parasympathetic division
Utilizes two neurons and one ganglion for each impulse
Sympathetic division
Especially important during fight-or-flight responses
Accelerates heartbeat and dilates bronchi
Active muscles require a ready supply of glucose and oxygen
getting ready for the fight
Parasympathetic division
Housekeeper
Promotes all internal responses associated with a relaxed state
Promotes digestion and retards heartbeat
more relaxing
Neurons and neuroglia
are the two principal types of cells in neural tissue.
Neurons (nerve cells)
Cell body
Dendrites
axon
cell body
contains nucleus and organelles
dendrites
receive signals from sensory receptors or other
neurons.
axon
conducts nerve impulsesto another neuron or to other cells
Covered by myelin sheath
Any long axon is also called a nerve fiber.
Astrocytes
help maintain neuron health.
Microglia
are phagocytic cells that remove bacteria and debris.
oligodendrocytes
in the CNS form the myelin sheath
Schwann cells
in the PNS perform this function.
Gaps are nodes of Ranvier.
Ependymal cells
line the ventricles of the brain, producing cerebrospinal fluid.
Satellite cells
surround neuron cell bodies in ganglia.
Participate in responses to injury
Types of Neurons
Sensory (afferent) neurons
Interneurons
Motor (efferent) neurons
Sensory (afferent) neurons
Accept impulses from sensory receptors
Transmit them to the CNS
Unipolar
Interneurons
Convey nerve impulses between various parts of the CNS Multipolar Form complex pathways in the brain Lead to higher mental functions Thinking Memory Language
Motor (efferent) neurons
Accept nerve impulses from the CNS
Transmit them to muscles or glands
Multipolar
Transmission of Nerve Impulses
Voltage is the measure of the electrical potential between two points.
Difference between electrode placed inside and another outside the axon
Membrane Potential
An electrical potential difference across a membrane is called a membrane potential
Resting Potential
The membrane potential when the axon is not conducting an impulse.
The inside of a neuron is more negative than the outside, around –70 mV.
Due in part to the activity of the sodium-potassium pump
Transmission Across a Synapse
A synapse is a region where neurons nearly touch.
The small gap between neurons is the synaptic cleft.
Transmission across a synapse is carried out by neurotransmitters.
Neurotransmitters
Acetylcholine
Norepinephrine
Dopamine
Serotonin
Acetylcholine
In CNS and PNS, excites skeletal but inhibits cardiac muscle
Norepinephrine
In CNS, important to dreaming, waking and mood
Dopamine
In CNS, involved in emotions, learning, and attention
Serotonin
In CNS, involved in thermoregulation, sleeping, emotions, and perception
Neurotransmitter Removal
The postsynaptic membrane contains enzymes to inactivate the neurotransmitter.
Acetylcholinesterase breaks down acetylcholine.
Short existence of neurotransmitters at synapse prevents continuous stimulation or inhibition of postsynaptic membranes
Synaptic Integration
A single neuron is on the receiving end of:
Many excitatory signals, and
Many inhibitory signals
Integration
The summing of excitatory and
inhibitory signals
drug abuse
Drug abuse – person takes a drug at a dose level that increases the potential for a harmful effect
Addiction – when more of the drug is needed to get the same effect
Withdrawal – when the user stops taking the drug
Alcohol, drugs, and tobacco can all adversely affect
the developing embryo, fetus, or newborn
