What are the components and functions of the nervous system.
- The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body.
- Together, these organs are responsible for the control of the body and communication among its parts.
Why do small organisms such as paramecium not have a nervous system?
- Paramecium do not have a nervous system as they are microscopic unicellular organisms that can transmit information through diffusion.
- However, once an organism gets to a larger size, more sophisticated means of transferring information are required.
- Hence, human beings are too large to use the mechanisms employed by Paramecium.
Describe the basic layout of the nervous system.
Describe the structure of a spinal cord segment.
- Rootlets come together to form roots.
- Sensory neurone comes from the dorsal nerve root.
- Motor neurone comes from the ventral nerve root
Describe the structure of the epineurium, perineurium, endoneurium and nerve fascicles.
- Bundles are called fascicles
- Each fascicle is surrounded by a connecting tissue layer called the Perineurium
- Individual nerve fibres inside the fascicle are held together by connecting tissue called Endoneurium
- Individual fascicles are held together by connecting tissue called the Epineurium
What are the two types of cells in the nervous system?
- Glial cells
What is the structure and function of astrocytes
- Create blood-brain barrier – prevents toxins/bacteria/pathogens getting from the blood to the brain.
- Do this by interacting with endothelial cells to create tight junctions.
- Extend processes out towards synapses and 'vacuum' up any spare transmitters.
Compare and contrast Schwann cells and oligodendrocytes.
- Schwann cells can only myelinate one axon
- An oligodendrocytes can myelinate many axons.
Describe the structure and function of microglia cells.
- Very thin branches processes
- Looking for things that can cause damage to brain
- Become activated if they find 'trouble'
- Turn into macrophage
Compare and contrast the sympathetic and parasympathetic nervous systems in terms of the overall function as well as its effects on the following:
- Salivary glands
- Sympathetic = fight or flight
- Parasympathetic = rest and digest
Describe the sympathetic features of the nervous system.
- Sympathetic nerve fibres innervate all vessels except capillaries and precapillary sphincters which follow local control.
- Sympathetic division prioritizes blood vessels to brain, skeletal muscles and heart in times of emergency.
- Blood vessels to skin vasoconstrict to minimize bleeding if injury occurs during stress or exercise.
- Venoconstriction increases cardiac return.
Identify the hormones of interest for different organs:
- Adrenal glands
- Adrenal medulla
- Liver: angiotensin and thrombopoietin
- Duodenum: CCK and secretin
- Kidney: renin and erythropoietin
- Stomach: gastrin and ghrelin
- Pancreas: insulin and glucagon
- Adrenal glands: glucocorticoids and mineralocorticoids
- Adrenal medulla: adrenaline and noradrenaline
What do hormones regulate?
Hormones control and regulate…
- Metabolism and energy balance
- Growth and development
- Body defences
- General homeostasis and water, nutrient, and electrolyte balance of the blood.
Categorise hormones according to their structural properties.
- Peptide hormones
- Steroid hormones
- Thyroid hormones
In light of the various categories of hormones, distinguish between them on the following basis:
- Synthesis and storage
- Transport in blood
- Location of receptor
- Response to receptor-ligand binding
Which processes are regulated and controlled by the hypothalamus?
- Heart rate, blood pressure
- Feeding and satiety
- Circadian rhythms
- Lactation (suckling/baby crying)
What does the hypothalamus produce?
- ADH and oxytocin that travel to posterior pituitary
- 6 hormones that travel via the hypothalamo-hypophyseal portal system to the anterior pituitary, 4 stimulatory, 2 inhibitory.
Discuss the structure of the pituitary gland (aka hypophysis)?
The pituitary is divided into two lobes
I. Anterior pituitary
II. Posterior pituitary
Outline the stress response.
- Stress is commonly defined as a state of real or perceived threat to homeostasis.
- Maintenance of homeostasis in the presence of aversive stimuli (stressors) requires activation of a complex range of responses involving the endocrine, nervous, and immune systems, collectively known as the stress response.
- Activation of the stress response initiates a number of behavioural and physiological changes that improve an individual's chance of survival when faced with homeostatic challenges.
- The principal effectors of the stress response are localized in the hypothalamus, the anterior lobe of the pituitary gland, and the adrenal gland.
Discuss the behavioural and physiological adaptations of the stress response.
- Behavioural effects of the stress response include increased awareness, improved cognition, euphoria, and enhanced analgesia.
- Physiological adaptations initiated by activation of this system include increased cardiovascular tone, respiratory rate, and intermediate metabolism, along with inhibition of general vegetative functions such as feeding, digestion, growth, reproduction, and immunity.
What are the two adrenal cortical hormones?
- Glucocorticoids (cortisol)
- Mineralocorticoids (aldosterone)
Briefly outline the control of the adrenal gland
- Fight or flight response
- Ramping up your blood pressure
- Dumping glucose into your bloodstream
- Shutting down non-emergency services
Differentiate between somatic and autonomic pathways.
In the autonomic nervous system, there are two neurones in relation to the CNS and effectors. Identify and describe them.
- Presynaptic neuron whose cell body is in CNS
- Postsynaptic neuron cell body in peripheral ganglion
Outline the role of chromaffin cells.
- The central portion of the adrenal gland, the medulla, is composed of chromaffin cells.
- The chromaffin cells are modified neurons.
- Numerous myelinated, presynaptic sympathetic nerve fibres pass directly to the chromaffin cells of the medulla.
- When nerve impulses carried by the sympathetic fibres reach the catecholamine-secreting chromaffin cells, they release their secretory products adrenaline and noradrenaline.
- Therefore, chromaffin cells are considered the equivalent of postsynaptic neurons.
- Because the chromaffin cells are considered the equivalent of postsynaptic neurones and they secrete into the blood stream this is another example of neurocrine secretion.
Compare and contrast the short term and more prolonged stress response of the adrenal glands
Outline the structure and function of the pineal gland.
- It produces melatonin (not melanin!)
- Melatonin is involved in control of circadian rhythm.
- Light exposure inhibits melatonin release.
- The neuronal pathway is from retina to hypothalamus to pineal gland.
- Melatonin inhibits release of gonadotrophins (LH and FSH).
- Perhaps most important thing to know is that it calcifies in early adulthood and is therefore visible on skull x-rays.
- The pineal gland is a midline structure.
Outline the portal blood supply to the anterior pituitary gland.
Outline the control of the thyroid gland in terms of the HPT axis.
- Hypothalamus releases TRH (Thyrotropin releasing factor), a stimulatory hormone, to the anterior pituitary gland.
- The anterior pituitary gland releases TSH (thyroid stimulatory hormone) to the thyroid gland.
- The thyroid gland releases T3 and T4
- If the thyroid hormones accumulate, negative feedback occurs by short loop and/or long loop inhibition
Based on the image below, answer the following questions.
- Which body region is this image of?
- How was the image obtained?
- Which plane has the head been 'cut' in?
- Can you label some white matter?
- Can you label some grey matter?
- Which substances appear black on this image?
- Where is the hypothalamus?
- How does the hypothalamus communicate to the rest of the body?
Correction: air and bone appears black.