Neurobiology 5 Flashcards
The autonomic nervous system
What is in the CNS?
-Brain
-Spinal cord
What is the PNS?
-Autonomic (involuntary) NS
-Somatic (voluntary) NS
What are the functions of the autonomic nervous system?
-Contraction/relaxation of smooth muscle.
-Exocrine and endocrine secretion.
-Control of the heartbeat.
-Steps in intermediary metabolism.
What is the autonomic nervous system made up of?
Cell body (in spinal cord or brainstem), preganglionic neurone, autonomic ganglion, postganglionic neurone, target organ/tissue.
-2 cells and 2 synapses
-presence of an additional synapse
-2nd axon goes to target organ
What is the somatic nervous system made up of?
Motor neuron, cell body (in spinal cord or brainstem), axon, neuromuscular junction and skeletal muscle.
What are the two branches of ANS?
-sympathetic
-parasympathetic
different functions, structures and reward receptors
What is the pre- and post-ganglionic transmitter of the sympathetic ANS?
Preganglionic transmitter: acetylcholine
Postganglionic transmitter: noradrenaline
Except: adrenal glands / sweat glands
What is the pre- and post-ganglionic transmitter of the parasympathetic ANS?
Preganglionic transmitter: acetylcholine
Postganglionic transmitter: acetylcholine
What occurs in the autonomic ganglia (outside CNS)?
What are the functions of the two branches of the ANS?
Parasympathetic:
-Rest and digest (satiation and repose)
Sympathetic:
-Fight or flight (stress, exercise response)
In some situations para and symp have opposing actions, but not in all
Both exert physiological control over the body under normal circumstances when the body is at neither extreme
What is the difference between the sympathetic and parasympathetic NS?
Parasympathetic NS has no paravertebral chain and has very short postganglionic chains.
What is the autonomic tone? Give examples.
Most tissues receive a basal level of autonomic activity. Active all the time.
E.g. blood vessels (sympathetic tone, partial constriction)
heart (vagal tone, decreases during exercise)- no vagus = higher heart rate
How is the autonomic nervous system controlled?
Autonomic (visceral reflexes)
-Sensory fibres (visceral afferents)
-Interneurons (in neural circuits in hypothalamus, brainstem / spinal cord)
-Sympathetic and parasympathetic pre/post-ganglionic neurones
-Effect organ i.e. eye, heart ect.
Give examples of autonomic reflexes.
-Baroreceptor reflex
-Lung inflation reflex
-Salivary
-Vomiting
-Defecation
-Micturition
-Defense reflex (fight or flight response)
Increase heart rate, cardiac output and blood pressure, increased blood flow to muscles.
What are autonomic reflexes controlled by? What is its affect?
Hypothalamus- stimulation produces autonomic response.
-Regulation of homeostasis
-Motivation emotional behaviour
-Damage to hypothalamus: failure of homeostatic mechanisms, can lead to failure in ANS.
What is the eye controlled by?
Both the parasympathetic and sympathetic NS.
What is accommodation?
Ciliary muscle contracts- near vision.
Ciliary muscle relaxes- far vision.
What is presbyopia?
Loss of near vision, as the lens becomes less elastic.
Describe the experiment of pupil dilation-arousal/stress.
Pupil size increases in proportion of the difficulty of a task.
Calculate 9 x 13 and pupil will dilate slightly. But if you do 29 x 13, they will widen further and remain dilated until you reach the answer or stop trying.
What happens with autonomic failure?
Autonomic failure (controls the heart)- dizziness, fatigue, blackouts, postural hypotension. Neurodegenerative disease.
E.g. Horner’s syndrome- droopy eye, face often red/hot. Asymmetric effect.
How does a reflex work?
Sensory input -> processing in the brain -> autonomic output
