Ch 41-42 Neural Signals and Systems Flashcards
Have many branched dendrites and a single long axon
Neurons
– extend from cell body of neuron
– specialized to receive stimuli & send signals to the cell body
Dendrites
– extends from cell body of neuron
– forms branches (axon collaterals)
– transmits signals into terminal branches which end in synaptic terminals
Axon
Fatty insulation around axons in vertebrates
Myelin Sheath
Glial cells forming myelin sheath in the PNS (formed by other glial cells In the CNS)
Schwann cells
Gaps in sheath between successive Schwann cells
Nodes of Ranvier
• Electrical signals transmit information along axons
• but not flow of electrons like in electrical wires
• Plasma membrane of resting neuron (not transmitting an impulse) is polarized (the 2 sides of membrane have different charges)
• Cytoplasm negatively charged relative to fluid outside
– due to different ion concentrations
• ion: charged molecule
• e.g. Na+, K+, Cl-, PO
• Difference in charges measured in voltage
Neuron Signals
- self-propagating depolarization wave that moves down the axon
- wave of opening and closing ion channels
- transmission of a nerve impulse is like burning a trail of gun powder
- action potential at one end generates action potential in adjacent areas
Nerve Impulse: Action Potential Wave
Involves entire length of axon plasma membrane
– takes place in unmyelinated neurons
Continuous Conduction
– Depolarization skips along axon from one Node of Ranvier to the next • more rapid than continuous conduction • takes place in myelinated neurons – Nodes of Ranvier • where axon is not covered by myelin • location of ion channels
Saltatory Conduction
• Junctions between two neurons
– or between a neuron and effector
Synapses
– gap junctions: physical connection by ion channels
– allows continuation of impulse
Electrical Synapses
– separation of neurons by synaptic
cleft (a space between cells)
– neurotransmitters: chemical messengers conduct the signal
• released by exocytosis
Chemical Synapses
Complex neural circuits are created by
convergence and divergence
Neural Circuits
Allows many information sources to affect a single nerve.
Convergence
Allows a single signal to reach many destinations.
Divergence
Allows an initial impulse to propagate continuing impulses • Important in -rhythmic breathing -mental alertness -short-term memory
Reverberating Circuit
– only stopped by a depleting of neurotransmitters or independent inhibitor stimuli
Positive feedback
– Cnidarians
– nerve net (nerve cells scattered in body)
– no central control organ
Nerve Net
– Echinoderms
– central nerve ring
– nerves extend to various parts of the body in network similar to nerve net
Radial Nervous System
• Ventral nerve cord, numerous ganglia
• Afferent and efferent lateral neurons
• Cerebral ganglia with specialized functional
regions (arthropods)
Annelids and Arthropods
Central Nervous System (CNS) – brain – spinal cord Peripheral Nervous System (PNS) – sensory receptors – neurons outside the CNS
Vertebrate Nervous System
• Protected by bone and 3 meninges (connective tissue)
1. dura mater
2. arachnoid
3. pia mater
• Cushioned by cerebrospinal fluid in subarachnoid space
Human CNS
4 types of Glial Cells of the CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal Cells
- physical & nutritional support to neurons - coordinate neuron activity (including learning)
- induce blood vessels to form the blood-brain barrier
- some serve as neural stem cells
Astrocytes
Myelin sheaths around axons in CNS
Oligodendrocytes
Mobile, phagocytic cells
Microglia
- line cavities in the CNS
- contribute to formation of cerebrospinal fluid
- can serve as neural stem cells
Ependymal Cells
- Transmits impulses to and from brain
- Controls many reflex actions
- White matter
- Gray matter
The Spinal Cord
Myelinated axons in bundles
White matter
Inside the white matter
– masses of cell bodies, dendrites, & unmyelinated axons
Gray matter
Parts of The Human Brain
Brain Stem Cerebellum Thalamus Hypothalamus Cerebrum
Medulla, pons, and midbrain
- and controls many involuntary processes
- e.g. heart rate, swallowing, coughing
- respiratory and sleep centers
- for visual and auditory reflexes
Brain stem
Second largest division
-for muscular coordination and refinement of movements
Cerebellum
Between brain stem and cerebrum -sort and interpret all sensory information (except olfaction) before relaying to cerebrum
Thalamus
Below thalamus; connected to pituitary gland
-control of body temperature, appetite, fat metabolism, some emotions, pituitary gland
Hypothalamus
Largest division
Cerebrum
• Affects emotional aspects of behavior – motivation – sexual activity – autonomic responses – biological rhythms
Limbic System
Feeling states experienced spontaneously
– humans are born with capacity for fear, anger, sadness, happiness
– limbic system is present in all mammals
Emotions
Center of intellect, memory, consciousness, language
-controls sensation and motor functions
Divided into right and left hemispheres
- each with four lobes
The Cerebrum
Outer gray matter in brain
- divided into
1) motor,
2) sensory,
3) association areas
Cerebral cortex
Myelinated axons of neurons that connect regions of the brain
- inner part of brain, unlike in spinal cord
- Corpus callosum
White matter
Large band connecting hemispheres
Corpus callosum
Functional Areas of the Cerebrum
Occipital lobes
Temporal lobes
Parietal lobes
Frontal lobes
Visual centers
Occipital lobes
Hearing centers
Temporal lobes
- Somatosensory area:
- touch, pressure, heat, cold, pain
- Integration of sensory input
Parietal lobes
- Motor areas:
- control skeletal muscles
- Prefrontal cortex:
- an association area
Frontal lobes
– process by which information is encoded, stored, and retrieved
– can be conscious or unconscious (e.g. motor skills)
– can be stored in many regions
Memory
– recalls information (such as telephone number) for a few minutes
– possibly caused by reverberating circuits
Short-term memory
Information can be transferred from short-term memory to
long-term memory and learning
Enables changes in behavior
– nervous system changes in response to experience
– includes learning to walk, ride a bicycle, a new language
Neural plasticity
Process of acquiring knowledge or skills as a result of experience
Learning
Ability of nervous system to modify synapses
– allows learning and remembering
– probably the major form of neural plasticity
Synaptic plasticity
An alteration of consciousness
– decreased electrical activity in the cerebral cortex
– from which a person can be aroused
Sleep
– electrical activity of cerebral cortex slows
– metabolic rate slows
non-REM sleep
– characterized by rapid eye movement, dreams
- high brain activity
REM sleep
- The amount of time asleep varies greatly in mammals, from 3 h in the donkey up to 20 h in the lion, sloth, & armadillo.
- Recent data are consistent with trade-offs between sleep and foraging time.
Function of Sleep is Not Known
Many drugs alter mood by increasing or
decreasing the ________ of specific
neurotransmitters within the brain
concentrations
Habitual use of mood-altering drugs can
result in
psychological dependence
addiction
– body ’s response to the drug decreases
– greater amounts needed for desired effect – THIS INCLUDES CAFFEINE
Tolerance
Consists of sensory receptors and nerves
Peripheral Nervous System
– responds to changes in external environment
Somatic division
– regulates internal activities of the body
Autonomic division
In the PNS neurons are grouped into
Nerves
– >100 axons
– wrapped in connective
tissue
Nerve
– mass of neuron cell bodies
Ganglion
• has efferent nerves subdivided into sympathetic and parasympathetic systems • Organs are innervated by both sympathetic and parasympathetic nerves
– which function in opposite ways
• Example:
– sympathetic system increases heart rate
– parasympathetic system decreases heart rate
Autonomic System
