8.1/8.2/8.3/8.4 Flashcards
1
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Organization of Human Body Systems
A
cells–>tissues–>organs–>organ systems
2
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Circulatory and Lymphatic Systems
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Transports materials throughout the body and protects against disease along with the Immune System
3
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Digestive, Excretory and Respiratory System
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Add and/or remove substances from the blood.
4
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Integumentary Systems
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Communicate with brain and spinal cord and provide protection.
5
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Muscular and Skeletal Systems
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Enables body and its parts to move and provide protection.
6
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Nervous System
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Allows body to respond to external and internal stimuli.
7
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Endocrine System
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Chemical communication within the body.
8
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Reproductive System
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Produces and transports gametes and produces sex hormones.
9
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Homeostasis
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The tendency of the body to maintain a relatively constant internal environment.
10
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Why is homeostasis considered a dynamic process?
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Any given variable, such as body temperature, blood glucose levels, or blood oxygen levels, may rise and fall around an average value throughout the course of a day, but still be considered to be in balance.
11
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Feedback System
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A cycle of events in which a variable is continually monitored, assessed and adjusted.
12
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Three Components of a Feedback System
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Sensor, Control Center, Effector
13
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Sensor
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A body structure that monitors and detects changes in the internal environment.
14
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Control Center
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A body structure that sets the range of values within which a variable should be maintained, receives information from the sensor, and sends signals to effectors when needed.
15
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Effector
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A body structure that responds to signals from a control center to effect a change in a variable
16
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Two Types of Feedback Systems
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Positive and Negative
17
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Negative Feedback System
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Mechanism of homeostatic response by which the output of a system reverses a change in a variable, bringing the variable back to within normal range.
18
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How does Negative Feedback work?
A
- A sensor detects a change that disrupts a balanced state and signals a control center
- the control center then activates an effector, which reverses the change and restores the balanced state
19
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Examples of Negative Feedback Systems
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- body temperature
- blood glucose levels
20
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Positive Feedback System
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Mechanisms of homeostatic response by which the output of a system strengthens or increases a change in a variable.
21
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Examples of Positive Feedback Systems
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- blood clotting
- contractions during childbirth
22
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What must the body do to maintain homeostasis?
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The human body must respond to various internal and external stimuli, and it must regulate these responses.
23
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What is the Human Nervous System equipped to do?
A
Sense and respond to continuous change within the body and external environment.
24
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Function of the Nervous System
A
- Regulates body structures and processes to maintain homeostasis despite fluctuations in both the internal and external environment
- monitors and controls body processes
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Nerve Impulse
An electrochemical signal to or from the brain.
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What makes up the nervous system?
- brain
- spinal cord
- nerves that emerge from them and connect them to the rest of the body
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Central Nervous System
Network of nerves that includes the brain and spinal cord; integrates and processes information sent by nerves
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Peripheral Nervous System
Network of nerves that carry sensory messages to the central nervous system (CNS) and send info from the CNS to the muscles and glands; consists of the autonomic and somatic system.
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Involuntary Processes
Ones that do not require conscious control.
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Neurons
- nerve cell; the structural and functional unit of the nervous system
- specialized to respond to physical and chemical stimuli, to conduct electrochemical signals and to release chemicals that regulate various body processes
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Nerve
Message pathway of the nervous system; made up of many neurons grouped into bundles and surrounded by protective connected tissue.
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Glial Cells
Support cells of the nervous system that nourishes neurons, removes their wastes, defends against infection, and provides a supporting framework for all the nervous-system tissue.
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Four Common Features of All Neurons
Dendrites, Cell Body, Axon, Branching Ends
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Dendrites
Short, branching terminals that receive nerve impulses from other neurons or sensory receptors and relay the impulse to the cell body.
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Cell Body
Contains the nucleus and is the site of the cell's metabolic reactions; processes the input from the dendrites.
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Axon
Conducts impulses away from the cell body; range in length from 1mm to 1m (sciatic)
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Branching Ends
At the end of the axon; communicates with adjacent neurons, glands or muscles by releasing chemical signlas into the space between it and the receptors or dendrites of neighbouring cells.
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Myelin Sheath
The fatty, insulating layer around the axon of a nerve cell, composed of Schwann cells; protects myelinated axons and speeds the rate of nerve impulse transmission.
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How are neurons classified?
By their structure and function.
| *Number of processes that extend from the cell body*
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Three Types of Neurons Based of Structure
Multipolar, Bipolar, Unipolar
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Multipolar
- several dendrites
- single axon
- brain and spinal cord
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Bipolar
- single main dendrite
- single axon
- inner ear, retina of the eye, olfactory area of the brain
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Unipolar
- single process that extends from the cell body
- dendrite and axon are fused
- peripheral nervous system
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Three Types of Neurons Based on Function
Sensory Neurons, Interneurons, Motor Neurons
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Sensory Input
- sensory receptors, such as those in the skin, receive stimuli and form a nerve impulse
- sensory neurons transmit impulses from the sensory receptors to the central nervous system
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Integration
- interneurons are found only in CNS
- link between sensory and motor neurons
- process and integrate incoming sensory info
- relay outgoing motor info
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Motor Output
-motor neurons transmit info from the CNS to effectors including muscles, glands, and other organs that respond to impulses from motor neurons
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Reflexes
Sudden, involuntary responses to certain stimuli (eg. jerking hand away from hot object)
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Reflex Arc
Simple connection of neurons that results in a reflex action in response to a stimulus.
*usuallly involve only 3 neurons so it is rapid*
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How does the reflex arc work?
- it moves directly to an from the brain and spinal cord, before the brain centres involved with voluntary control have time to process the sensory info
* this is why pain is felt after when the brain has had time to process*
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How do neurons communicate?
- they use electrical signals to communicate with other neurons, muscles and glands
- involves changes in the amount of electric charge across a cell's plasma membrane
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Membrane Potential
Electrical charge separation across a cell membrane; a form of potential energy
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Resting Membrane Potential
Potential difference across the membrane in a resting neuron.
*About -70mV; negative on the inside of the cell relative to the outside*
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Three Factors that Contribute to Maintaining Resting Membrane Potential
- Large Protein Molecules
- Plasma Membrane Contains Ion-Specific Channels
- Sodium-Potassium Pump
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Large Protein Molecule
-negatively charged and are present in the intracellular fluid but not outside of the cell
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Ions in the Plasma Membrane
-ion-specifc channels that allow for the passive movement of ions, such as Na & K across the membrane
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Sodium-Potassium Pump
-actively transports Na+ and K+ in rations that leave the inside of the cell negatively charged compared to the outside of the cell
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Polarization
Lowering the membrane potential of the cell below its equilibrium value; in nerves, the process of generating a resting membrane potential of -70mV.
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Sodium-Potassium Pump
System involving a carrier protein in the plasma membrane that uses the energy of ATP to transport sodium ions out of and potassium ions into animal cells; important in nerve and muscle cells
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Step One of Sodium-Potassium Pump
The carrier protein has a shape that allows it to take up 3 sodiums ions.
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Step Two of Sodium-Potassium Pump
- ATP is split and a phosphate group (Pi) is transferred to the carrier protein
- a change in the shape of the carrier protein causes the release of 3 Na+ outside the cell
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Step Three of Sodium -Potassium Pump
The altered shape permits the uptake of 2 potassium ions (K+) from outside the cell.
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Step Four of Sodium-Potassium Pump
- the phosphate group is released from the carrier protein
- the change in shape of the carrier protein causes the release of 2 K+ into the cell
- the carrier protein is again able to take up 3 Na+, and the process repeats
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Why is it referred to as "resting" membrane potential when the Sodium-Potassium pump is constantly using energy to transport the ions?
- no nerve impulses are being transmitted along the axon
- the resting potential maintains the axon membrane in a condition of readiness for an impulse to occur
- energy for eventual impulses is stored in the electrochemical gradient across the membrane
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Depolarization
- when the cell becomes less polarized
- the membrane potential is reduced to less than the resting potential of -70mV
- the inside of the cell becomes less negative relative to the outside of the cell
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Action Potential
- the movement of an electrical impulse along the plasma membrane of an axon
- results in a rapid change in polarity across the axon membrane as the nerve impulse occurs
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Threshold Potential
A certain level of membrane potential that is reached, results in an action potential (usually close to -50mV)
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Characteristics of a Change in the Membrane Potential that Occur During an Action Potential
- occur within a period of a few milliseconds
| - occur in one small region of the axon membrane
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Step 1 of Changes in the Membrane Potential During Action Potential
-an action potential is triggered when the threshold potential is reached
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Step 2 of Changes in the Membrane Potential During Action Potential
- when threshold is reached, special structure in the membrane called voltage-gated sodium channels open and make the membrane very permeable to sodium ions
- the sodium ions on the outside of the axon suddenly move down their concentration gradient and rush into the axon
- Within a millisecond or less, enough positively charged sodium ions have crossed the membrane to make the potential difference across the membrane in that tiny region of the axon at +40mV
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Step 3 of Changes in the Membrane Potential During Action Potential
- As a result of the change in membrane potential, the sodium channels close and voltage-gated potassium channels open
- Potassium now moves down their concentration gradient toward the outside of the axon, carrying positive charge out of the neuron
- As a result, the membrane potential becomes more negative again, in fact, the membrane potential becomes slightly more negative than its original resting potential, becoming HYPERPOLARIZED to about -90mV
- At this point, the potassium channels close
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Step 4 of Changes in the Membrane Potential During Action Potential
-The Na+/K+ pump and the small amt of naturally occurring diffusion quickly bring the membrane back to its normal resting potential of -70mV (REPOLARIZATION)
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Refractory Period
A few milliseconds after an action potential, the membrane cannot be stimulated to undergo another action potential
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What occurs after the process of action potential?
-the entire process continues down the length of an axon until it reaches the end, where it initiates a response at the junction with the next cell
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Nodes of Ranvier
-exposed areas of myelinated neurons that occur at regular intervals
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Myelinated Nerve Impulse
With myelin sheath, action potential conduction along axons is much quicker because it jump's from Node of Ranvier to Node of Ranvier
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Saltatory Conduction
The conduction of an impulse along a myelinated neuron due to the myelin sheath
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Synapse
Junction between two neurons or between a neuron and an effector (muscle or gland)
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Neuromuscular Junction
Synapse between a motor neuron and a muscle cell.
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Synaptic Cleft
Small gap between neurons.
| -0.02 micrometers wide (neurons are not close enough for the impulse to jump from one to the other)
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Neurotransmitters
Chemical messenger secreted by neurons to carry a neural signal from one neuron to another, or from a neuron to an effector, such as a gland or muscle fibre.
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How do neurotransmitters work?
- When action potential arrives at the end of a presynaptic neuron, the impulse causes intracellular sacs that contain neurotransmitters to fuse with the membrane of the axon and release their contents into the synaptic cleft by exocytosis
- The neurotransmitters diffuse across the synapse to reach the dendrites of the postsynaptic neuron, or cell membrane of effector (0.5 to 1.0 ms)
- Neurotransmitter binds to specific receptors on postsynaptic membrane triggering and ion-specific channels to open
- If this depolarizes cell to threshold potential, another action potential occurs and the impulse will travel along post synaptic neuron and so on…
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What effects do neurotransmitters have on the post-synaptic membrane?
Either excitatory or inhibitory effects.
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Excitatory
- causes opening of channels allowing positive ions e.g. sodium to flow into postsynaptic neuron
- causes depolarization
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Inhibitory
- causes opening of channels e.g. potassium channels, allowing potassium to flow out
- causes hyperpolarixation
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Acetylcholine
The primary neurotransmitter of both the somatic nervous system and the parasympathetic nervous system.
87
Dopamine
- affects the brain synapses in the control of body movements; linked to sensations of pleasure such as eating
- Excessive production linked to schizophrenia; inadequate production linked to Parkinson’s disease
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Serotonin
- regulates temperature and sensory perception, involved in mood control
- inadequate amounts linked to depression
89
Endorphins
- act as natural painkillers in the brain; also affect emotional areas of the brain
- Deficiency linked to an increased risk of alcoholism
90
Norepinephrine
- used by brain and some autoimmune neurons; complements the actions of the hormone epinephrine, which readies the body to respond to danger or other stressful situations
- Overproduction linked to high blood pressure, anxiety, and insomnia; deficiency linked to hunger cravings and exhaustion
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Brain
Coordinating center of the nervous system.
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Grey Matter
- contains mostly cell bodies, dendrites and short, unmyelinated axons
- found around outside areas of the brain and forms H-shpaed core of the spinal cord
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White Matter
- contains myelinated axons that run together in tracts
| - forms the inner region of some areas of the brain and the outer area of the spinal cord
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Spinal Cord
Carries sensory nerve messages from receptors to brain and relays motor nerve messages from brain to muscles, organs and glands.
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What is the delicate tissue of the spinal cord protected by?
Cerebrospinal Fluid, Soft Tissue Layers and the Spinal Column
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Cerebrospinal Fluid
Dense, clear liquid derived from blood plasma, found in the ventricles of the brain, in the central canal of the spinal cord, and in association with the meninges; transports hormones, white blood cells , and nutrients across the blood-brain barrier to the cells of the brain and spinal cord; acts as a shock absorber to cushion the brain.
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Three General Regions of the Brain
Hindbrain, Midbrain, Forebrain
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Meninges
Three layers of tough, elastic tissue within the skull and spinal column that directly enclose the brain and spinal cord.
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Olfactory Lobes
-receive info about smell
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Cerebum
-paired giant hemispheres, major co-ordinating centre; speech, reasoning, memory, personality
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Cerebral Cortex
- surface of cerebrum, composed of grey matter
| - linked with activities associated with thinking and feeling
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Corpus Callosum
-bundle of white matter that joins the two hemispheres and allows communication between them
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Thalamus
Coordinates and interprets sensory info and directs it to the cerebrum.
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Hypothalamus
Direct connection to pituitary gland unites nervous system and endocrine system.
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Frontal Lobe
- motor areas control movement of voluntary muscles
| - intellectual activities and personality
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Temporal Lobe
- Sensory areas are associated with vision and hearing
| - memory and interpretation of sensory info
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Parietal Lobe
- sensory areas are associated with touch and temperature awareness
- linked to emotions and interpreting speech
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Occipital Lobe
- sensory areas are associated with vision
| - interpret visual info
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Midbrain
- consists of four spheres of grey matter
| - acts as relay centre for some eye and ear reflexes
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Cerebellum
-controls limb movements, balance, muscle tone
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Pons
-largely a relay station passing information between the two regions of the cerebellum and between cerebellum and medulla
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Medulla Oblongata
- joins brain to spinal cord
| - works to maintain homeostasis
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Blood-Brain Barrier
Protective barrier formed by glial cells and blood vessels that separates the blood from the central nervous system; selectively controls the entrance of substances in the brain from the blood.
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Right Brain
Associated with holistic and intuitive thinking, visual-spatial skills, and artistic abilities.
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Left Brain
Linked to segmental, sequential, and logical ways of thinking and to linguistic and mathematical skills.
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Peripheral Nervous System
Network of nerves that carry sensory messages to the central nervous and send info from the CNS to the muscles and glands.
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Two Divisions of The Peripheral Nervous System
Autonomic and Somatic
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What kind of control is the Somatic system under?
Voluntary
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What areas do the neurons of the somatic system service?
Head, trunk, limbs
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Somatic System
In vertebrates, division of the peripheral nervous system that controls voluntary movement of skeletal muscles.
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What does the somatic system include?
12 pairs of cranial nerves and 31 pairs of spinal nerves (all myelinated)
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What are the cranial nerves mostly associated with?
Functions in the head, neck, and face.
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Autonomic System
In vertebrates, the division of the peripheral nervous system that controls involuntary glandular secretions and the functions of smooth and cardiac muscle.
-maintains homeostasis
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What kind of control is the autonomic system under?
Involuntary
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What do the nerves of the autonomic system control?
Stimulate or inhibit the glands of the cardiac or smooth muscle.
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How does the autonomic system maintain homeostasis?
Adjusts the body to variations in the external and internal environments without the individual having to think about it and control it consciously.
127
What is the autonomic system controlled by?
Hypothalamus and medulla oblongata.
128
Two Divisions of Autonomic System
Sympathetic and Parasympathetic
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Sympathetic Nervous System
Regulates involuntary processes in the body; works in opposition to the parasympathetic nervous system; typically activated in stress-related situations.
130
What is another name for the sympathetic nervous system?
Fight or Flight
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What do sympathetic neurons release?
Norepinephrine
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Norepinephrine
Neurotransmitter released by sympathetic neurons to produce an excitatory effect on target muscles.
133
What else is released during fight or flight?
Adrenal glands release epinephrine and more norepinephrine which function as hormones to activate stress response.
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Bodies Response to Fight or Flight
Increased blood pressure and heart rate, digestion slows, bladder sphincter constricts, feeling of anxiety
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Parasympathetic Nervous System
Regulates involuntary processes in the body; works in opposition to the sympathetic nervous system; typically activated when the body is calm and at rest
136
What is another name for the parasympathetic system?
Rest and Digest
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Functions of the parasympathetic system?
- restores and conserves energy
- slows heart rate
- reduces blood pressure
- promotes digestion of food
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What neurotransmitter is used by the parasympathetic system?
Acetylcholine which control organ responses
