Homeostasis and autonomic nervous system Flashcards
What are the 5 steps in homeostatic balance?
- stimulus
- receptor
- input
- output
- response
What is homeostasis?
the maintenance of relatively stable internal conditions despite continuous changes in the environment.
What is dynamic state of equilibrium?
a balance or steady state, in which internal conditions are constantly adjusting to changes but kept within relatively narrow limits.
What is law of mass balance?
a steady state in which the total amount of a substance the body takes in must be equal to the amount it loses
- ensures total amount of substance in body remains constant
What are the 2 main regulator organs and what is the variable?
- nervous and endocrine
V: the factor being regulated in the system (blood sugar, body temp etc.)
What are the 3 homeostatic control variables?
receptor, control center, effector
Explain receptor, control center and effector.
R(sensor): Monitors environment, responds to stimuli—changes in a variable that evoke a response, Sends information to the control center (input)
C: Receives input from receptor, determines set point (range of levels which a variable is maintained) and appropriate response to input, sends information to the effector (output)
E: Receives output from control center, provides the means to respond (via muscle or gland), response either reduces (negative feedback) or enhances (positive feedback) the effect of the stimulus
What is a negative feedback mechanism?
Uses the afferent and efferent pathways
- response reduces or shuts off original stimulus
- variable changes in the opposite direction of initial change, bringing it back to original state
What are some examples of negative feedback?
- regulation of body temperature (nervous system)
- regulation of blood glucose by insulin (endocrine system)
What is a positive feedback mechanism?
Response enhances or exaggerates the original stimulus
- change in the same direction of initial change
Examples of positive feedback.
- enhancement of labor contractions by oxytocin
- platelet plug formation and blood clotting
What is homeostatic imbalance?
a disturbance of homeostasis
- increases risk of disease
- contributes to changes with aging (system becomes less effective)
- if negative is overwhelmed, positive may take over (e.g., heart failure)
What is the automatic nervous system (ANS) also called and visceral motor system?
- involuntary NS
consists of motor neurons that: - innervate smooth and cardiac muscles and glands
- adjusts to ensure optimal support (heart rate, blood pressure, digestive processes)
- operate via subconscious control
What is different between the somatic and autonomic nervous system?
- effectors
- number of neurons between CNS and the effectors
- actions of their neurotransmitters at the effectors
Describe the SNS.
- cell body is in CNS and a single, thick myelinated group A axon extends in spinal or cranial nerve directly to skeletal muscle
What are the 2 pathways in the ANS?
- preganglionic neuron: cell body in CNS with thin, lightly myelinated preganglionic axon extending to ganglion
- postganglionic neuron (outside CNS): cell body synapses with preganglionic axon in autonomic ganglion with nonmyelinated postganglionic axon that extends to effectors
What is released in the ANS and what is their effect?
preganglionic fibers: release ACh
postganglionic fibers: release norepinephrine (sym) and ACh (para)
- can be excitatory or inhibitory - depending on the receptor
what fibers do most spinal and cranial nerves contain?
somatic and autonomic fibers
What are the 2 arms of the ANS?
Parasympathetic division: promotes maintenance functions, conserves energy
Sympathetic division: mobilizes body during activity
What is dual innervation?
all visceral organs are receive input from both (para and sym), they are both partial active to counter balance and maintain operations
- Dynamic antagonism between two divisions maintains homeostasis
What does the sympathetic system do?
- mobilizes body during activity
- fight- or - flight
- exercise, excitement, emergency and embarrassment activate SS
- Effects: heart rate, dry mouth, sweaty skin, dilated pupils, increased blood pressure, dilated bronchioles, liver releases glucose.