Topic 2: The ANS Flashcards
This directs the “flight or fight or freeze” response of the ANS
The Hypothalamus
Monitors blood glucose levels, the body’s water content, Circadian rhythm regulates appetite, sleep and sexual behaviour as well as controlling body temperature.
The Hypothalamus
The Hypothalamus also controls hormones released from the pituitary gland Including…
Oxytocin and Antidiuretic Hormone (ADH)
Plays a role in uterine contractions during childbirth and breast feeding. its secretion can be caused by the sound of a baby crying.
Oxytocin
This hormone is responsible for increasing water absorption in the collecting ducts of the kidney. It also increases arterial blood pressure.
Antidiuretic Hormone (ADH)
The hypothalamus will release this hormone in the morning just before waking to increase blood glucose levels to counterbalance the potentially harmful effects of not eating or drinking while asleep
Cortisol
What is the HPA Axis?
Hypothalamus, pituitary, and adrenal cortex alliance
This hormone is released which has widespread actions which help restore homeostasis after stress.
Cortisol
Partly responsible for for creating euphoria and pain inhibition. It works with epinephrine to create memories of short-term emotionally significant events (flash-bulb memories) to remember what to avoid in the future. (these memories can sometimes be inaccurate)
Cortisol
The effects of chronic cortistol secretion:
Damage to cells in the hippocampus resulting in impairedorsosis
Difference between short term stress response vs chronic stress response of the HPA axis:
Short term: arouses immunological memory for the invaders
Chronic: supresses the ability of the immune system to do its job
The ANS (aka Visceral System) involves the
control of the heart, gland, and smooth muscles of the body. Since for the most part, it is not subject to voluntary control, it is also known as the involuntary system.
The ANS works together with the ______ ______ to control the secretion of hormones and is itself controled by the hypothalamus. Its effects include secretions from the _______ ______
Endocrine System;
Exocrine Glands
True or False: The ANS is an efferent system.
True
Motor Fibers make up the bulk of the ANS, although it does include afferent axons that carry information from the viscera
The motor component of these reflexes may also involve the SNS for example salivating and vomitting.
Simple reflexes are completed entirely within the organ concerned, whereas more complex reflexes are controlled by the higher autonomic centres in the CNS, principally the hypthalamus.
examples of how the ANS effects often involve reflexes
Comparison of ANS & SNS
Control:
SNS: Voluntary – ANS: Involuntary
Effectors:
SNS: Skeletal mm – ANS: Cardiac & Smooth mm; glands
of neurons in the motor pathway:
SNS: 1 LMN from CNS synapses directly with skeletal mm
ANS: 2 motor neurons in a series
The ANS is divided into two divisions (on the basis of anatomical and functional differences) called
The Parasympathetic and Sympathetic
T or F: most organs are innervated by fibres from both divisions and the influence is usually antagonistic
True; example: the PNS slows the heart while the SNS increase its rate and contractility
T or F: The sympathetic nervous system is not only associated with “flight or fight” reactions but overall homeostasis as well being essential for maintaining the fundamental vital activities of an organ. It will always be active at a basal level(sympathetic tone)
True;
It becomes more active during times of stress and its action during the stress response comprise the flight or fight response.
Where are parasympathetic nerve cell bodies located
Theyre located in different nuclei throughout the brain stem, as well as a few nuclei in the sacral region of the spinal cord. (sacrocranial division)
In the medulla, the cranial nerves III, VII, IX, and X (3,7,9,10) form the
preganglionic parasympathetic fibers
The preganglionic fiber from the medulla or spinal cord projects to ganglia very close to the target organ and makes a synapse. This nerve carries most of the PANS (parasympathetic) signals
CN X (vagus)
The sympathetic nerve cell bodies of a preganglionic (presynaptic) neuron are always in the CNS within the ________.
Lateral horn.
Every preganglionic sympathetic neuron orginates at these levels. There are no exceptions, which is why the sympathetic division is also known as the thoracolumbar division of the ANS
Paravertebral Ganglia (sympathetic trunk) are
paired chains of ganglia connected by nerve fibers that extend from the base of the skull to the Coccyx.
Paravertebral Ganglia (pre-aortic ganglia)
Lie directly anterior to the vertebral column and
are cemented on the anterior aorta
2 celiac ganglia (solar plexus) are situated behind the stomach and supply the organs in the abdomen. Celiac plexus block is sometimes used to treat intractable pain from cancers such as pancreatic cancer.
Preganglionic Fibres and The Adrenal Medullae
Preganglionic axons go directly to the adrenal medulla where synapse on cells releasing noradrenalin and adrenalin into the blood. Since every cell of the body can be affected by these hormones, this allows sympathetic access beyond those cells which have direct post ganglion sympathetic fibres innervating them
Vasovagal Syncope =
Fainting
A paroxysmal condition marked by a slow pulse, fall in blood pressure, and sometimes convulsions. It is though to be a sudden stimulation of the Vagus nerve mediated through baroceptors in the carotid sinus, the aortic arch, or the heart
Vasovagal Syncope
A paroxysmal condition marked by a slow pulse, fall in blood pressure, and sometimes convulsions. It is though to be a sudden stimulation of the Vagus nerve mediated through baroceptors in the carotid sinus, the aortic arch, or the heart
Vasovagal Syncope
Information passed on to the higher centers like the hypothalamus results in simultaenous enhancement of PANS (vagal) tone and withdrawal of SYNS tone
The two most common causes of Vasovagal Syncope
Orthostatic hypotension aka postural hypotension which is a drop in BP that occurs when a person who was sitting or lying down suddenly stands.
Postprandial hypotension, a drop in BP within one hour of eating a meal. In clinically stable, unmedicated elderly person, blood pressure decreases significantly after morning and noon meals. Such decreases do not occur in younger persons.
Thought to be due to impaired baroreflex compensation for low BP. Splanchnic blood pooling during digestion and lower limb blood pooling in the lower limb on standing are the triggers.
Postprandial hypotension and postural hypotension
Comes with rapid emptying of the urinary bladder. Typically these episodes follow lots of beer or while passing water in the middle of the night
Micturation Syncope
The Stellate ganglion’s AKA and location
Cervicothoracic ganglion is a sympathetic ganglion of the paravertebral chain of ganglia located superior to the neck of the 1st rib
May be cut in order to decrease the symptoms of exhibited by Raynaud’s phenomenon and hyperhydrosis of the hands
The Stellate ganglion
