ch 8 Flashcards
define homeostasis
equilibrium between an organism’s physiological functions + between the organism and its environment
homeostasis is a balance in response to continually changing conditions in both the ___ and ___ environments
internal and external
define dynamic equilibrium
when an organism remains stable with fluctuation limits
when an organism can’t maintain its balance:
death
3 components of homeostatic control centres
- monitor
- coordinating centre
- regulator
3 components of homeostatic control centres: MONITOR
special sensors in the organs that detect changes in homeostasis
3 components of homeostatic control centres: COORDINATING CENTRE
receives message from sensors and relays info to appropriate regulator
3 components of homeostatic control centres: REGULATOR
organ/tissue that restores normal balance
process of homeostatic control system
- stimulus disrupts homeostasis
- (controlled condition monitored by) receptors send to control centre
- control centre provides effectors that respond to alter condition
- return to homeostasis when response brings controlled condition back to normal
the activity of some specialized parts of an animal are coordinated by the TWO MAJOR SYSTEMS OF INTERNAL COMMUNICATION:
- nervous system (involves high-speed messages)
- endocrine system (involves production, release, and movement of chemical messengers)
all animals exhibit coordination by chemical signals: ___, ___, and __
- hormones
- pheromones
- neurotransmitters
chemical signals: hormones
- produced by endocrine system
- communication between organs of the body
chemical signals: pheromones
- communicate between different individuals
chemical signals: neurotransmitters
- between cells, locally (short distances; between neurons)
negative feedback systems prevent
small changes from becoming too large
negative feedback systems:
- most homeostatic control systems (body self correcting)
- response is opposite to stimulus
- decreases an action, stops when back to normal
positive feedback systems ___ a small effect
amplify
positive feedback systems:
- response is same as stimulus
- leads to instability and possibly death
- must be turned off by outside event
positive feedback system: example
- blood clotting
- childbirth
negative feedback system: example
- if body temperature changes, system restores normal levels
- Blood sugar regulation: insulin lowers blood glucose when levels are high
the brain is the ___ of the body
control centre
brain + nervous system:
- uses nervous system as interface w external environment and control system for internal environment
- monitors and controls bodily processes
- brain, spinal cord, and nerves that emerge and connect to rest of body
- brain contains more than 100 billion nerve cells (each nerve can have up to 10,000 connections w other nerve cells)
nervous system divided into
- central nervous system (CNS) (brain and spinal cord) (integrates and processes info from nerves)
- peripheral nervous system (PNS) (network of nerves carrying sensory messages to CNS and sending info from CNS to effectors: muscles and glands) (subdivisions: AFFERENT and EFFERENT systems)
PNS: afferent system
carries TOWARDS
- receives input from receptors and transmits to CNS by AFFERENT NEURONS (sensory neurons: carry impulses from sensory receptors to CNS)
PNS: efferent system
carries AWAY
- efferent neuron carries impulses from CNS to effectors (muscles + glands)
- further subdivided into SOMATIC and AUTONOMIC systems
PNS: efferent system: SOMATIC SYSTEM
made of efferent (motor) neurons that carry signals to skeletal muscles in response to external stimuli
PNS: efferent system: AUTONOMIC SYSTEM
controls involuntary processes
- communicates w effectors (smooth muscles and glands)
- further divided into SYMPATHETIC and PARASYMPATHETIC NERVOUS SYSTEM
PNS: efferent system: autonomic system: SYMPATHETIC DIVISION
- increases energy consumption and prepares body for action
- dominates in situations with STRESS, danger, excitement, strenuous physical activity
PNS: efferent system: autonomic system: PARASYMPATHETIC DIVISION
- stimulates body activities that acquire and conserve energy
- dominates during quiet, low-stress situations (e.g. relaxation)
two kinds of cells in nervous system:
neurons/nerve cells and glial cells
cells of nervous system: NEURONS/nerve cells
- structural + functional (specialization: respond to physical/chemical stimuli, conduct electrochemical signals, release chemicals that regulate body processes)
- made of nucleus, cell body, dendrites, axons
- organized into nerves (tissues)
neurons have the same features as
other body cells (cell membrane, cytoplasm, etc)
- types differ in shape, size, but share four common features
common features among neurons:
- dendrites (dendros = tree)
- cell body
- axon
- axon terminal (branching ends)
common features among neurons: DENDRITES
branched projections which form TREELIKE OUTGROWTH at one end of neuron
- receive nerve impulses/signals and transmit towards cell body
common features among neurons: CELL BODY
contains nucleus and most organelles
- site of cell’s metabolic reactions
- processes input from dendrites (if input is big enough, it’s relayed to axon and an impulse is initiated)
common features among neurons: AXON
specialized projection that conducts impulses away from cell body to another neuron/effector
- terminal end branches into fibres
- branching end as small button-like swellings: AXON TERMINALS
most axons are bundled together as NERVE FIBRES/NERVES
- nerves branch to relay signals throughout periphery of ENTIRE BODY
common features among neurons: AXON TERMINAL (branching ends)
releases chemical signals into space between neuron and receptors/dendrites of neighbouring cells
what are nerves
- variously-sized many axons that form nerve fibres
- branch extensively to relay signals throughout periphery of entire body
neuron support system: glial cells
- support cell of nervous system
- do not conduct electrical signals
- nourish neurons, remove their wastes, and defend against infection
- provides a supporting framework for all nervous system tissue
neuron support system: glial cells: SCHWANN CELLS (main glial cells)
- form myelin by wrapping themselves around axons
neuron support system: glial cells: MYELIN SHEATHS (formed by glial cells)
- fatty, insulating layer around axons (gives them white, glistening appearance)
- protects neurons and speeds up the rate of nerve impulse transmission
neuron support system: glial cells: NODEDS OF RANVIER
- regularly occurring gap between sections of myelin sheaths along axon
- expose axon membrane directly to extracellular fluids
- speeds up the rate at which electrical impulses move along axons
neural signalling
communication by neurons
- reception, transmission, integration of nerve impulses by neurons and response to these impulses
neural signalling process: reception
detection of stimulus, performed by neurons and by specialized sensory receptors (in eyes and skin)
neural signalling process: transmission
movement of message along neuron to either another neuron or muscle or gland
neural signalling process: integration
sorting and interpretation of multiple neural messages and determination of appropriate response
neural signalling process: response
output or action
neural signalling process: THREE FUNCTIONAL CLASSES OF NEURONS:
- afferent neurons (sensory neurons)
- interneurons
- efferent neurons
neural signalling process: THREE FUNCTIONAL CLASSES OF NEURONS: afferent neurons (sensory neurons)
transmit stimuli collected by their sensory receptors to interneurons in CNS
neural signalling process: THREE FUNCTIONAL CLASSES OF NEURONS: interneurons
integrate neural message and relay impulses between afferent and efferent neurons, found primarily in brain and spinal
