Flashcards in Chapter 5 Deck (69):
Where does the motor cortex lie?
In front of the the Central sulcus. Therefore, it is also known as the precentral gyrus.
What does simulation of the motor cortex do?
The simulation of the motor cortex causes the opposite side of the body to react. The part depends on the area of stimulation.
Write down the representation of the body in the motor cortex from the medial to lateral side.
Foot, leg, thigh, hip, trunk, shoulder, elbow, hand, fingers, neck, brow, eye face, lips, jaw, tongue, swallowing muscles and chewing muscles.
What is the path of the corticospinal tract?
The corticospinal tract carries fibres mostly from the motor cortex and little from other areas. It forms a part in f the internal capsule, goes through the cerebral peduncle, through the pons, medullary pyramids and at the caudal end of the hindbrain, most of the fibres decussates.
What are striated and smooth muscles?
Striated muscles are voluntary muscles, because they appear striped. The smooth muscles are involuntary muscles and they are not striped. The heart, however, is made up of striated muscles even though it is not under voluntary control.
What are the different types of effector systems?
The somatic motor control is a single motor neuron that makes direct synapse on the target.
The autonomic preganglionic system is where the neuron stimulates a ganglia which acts on a spread area. Sympathetic motor neuron system is where the neuron stimulates the adrenal medulla which secretes hormones into the bloodstream causing widespread action. The last system is called the neuroendocrine system where neurons are designed to directly secrete chemicals into the blood.
What makes the motor system?
Even though the precentral gyrus is the most important motor component of the brain, the activity of it is strongly influenced by the pallium, striatum, cerebellum and many other cortical areas.
How does the parts of the motor cortex work?(vague version)
The different cortical areas including the precentral gyrus makes a committee decision which is finally enabled by the striatum and pallidum.
Where is the supplementary motor cortex located and what is its role?
The supplementary motor cortex lies in medial part of the cerebrum in front of the lower limb part of the motor cortex. Its role is to plan and sequence complex movements.
What is the Broca's area?
Broca's region is a library that manages the movement of the jaw and tongue for speech and the movement of the fingers for writing. It is mostly present in the left hemisphere of people. In right handed people, it is always left hand side, whilst in left handed people it can be either.
What happens when the corticospinal tract is damaged?
When the corticospinal tract is cut at the level of the hindbrain, the fine movements of the fingers are lost. The opposite hand to the damaged side always finds it impossible to sew, write and pick small objects. If this lesions was accompanied by lesion to the striatum, the person will be affected by increased spasticity and hypereflexia.
What are modules?
Functional systems in the hindbrain and spinal cord where the neurons are connected in a particular fashion to do semiautomatic functions. There are modules for walking, running, and chewing. These allows us to concentrate on higher cognitive functions. It also improves efficiency as the motor cortex does not need to connect to every single muscle directly.
What is the hierarchy of modules?
Modules are arranged such that the basic survivals learnt over the million year vertebrae evolution is given higher priority. These module encompasses eating, drinking, defensive behaviours, and movement patterns to explore the immediate surrounding.
How does the module system work?
The cerebral cortex conveys the request to the hypothalamus which checks and organises the modules or refuses due to inappropriate environmental condition. This information is then relayed to the cerebral cortex or the midbrain. If the modules are fine, the midbrain will initiate the pattern by stimulating the inbuilt pattern in the hindbrain or the spinal cord which uses the visceral motor, somatic motor or both to achieve the request.
How is the hypothalamus separated and how are the behaviours attributed each part?
The hypothalamus is split into a medial and the mammillary bodies and the adjacent parts of the midbrain(the substantia nigra and the ventral tegmental area.
The medial part are responsible for defence, reproduction and ingestion. This area includes the VMH(ventromedial nucleus).
The second group of areas are responsible exploratory and foraging behaviours, running and other means of locomotion to explore the surroundings.
How are modules otherwise useful?
Modules make intrinsic patterns of reflexes that aims at eliminating a painful stimulus or avoiding it.
Where are the main modules found?
The brainstem has modules for movement of the head and the neck, chewing, licking, facial expression, vocalisation and control of breathing.
The spinal cord has modules for locomotion, posture, reaching and grasping.
What are the some control descending pathways other than corticospinal tract?
Serotonin fibres from the raphe nuclei
Noradrenaline fibres from the locus coeruleus
What is the red nucleus and its role?
The red nucleus is a nucleus in the midbrain that is found in almost all animals that is responsible for the control of movement of the limbs. It is red due to high amounts of iron deposit in that area.
What is the raphe nuclei and its role?
The raphe nuclei is a nuclei in the hindbrain, which manufactures serotonin. Serotonin is involved in regulations of mood, the control of pain and regulation of the sleep-wake cycle.
what is the role of the cerebellum?
The cerebellum is concerned with coordination and correction of moment for the most efficient use of the body's resources and eliminate possible damage. It compares the actual position of the body to the required position and alters certain things to maintain posture and balance.
Why is the cerebellum important in humans and primates?
It is important in humans because we have the most binocular vision and the ability to use our fingers for precise and skilled movement. This requires the cerebellum for the fine and smooth control.
In other primates, their lives depend on the cerebellum to correctly execute acrobatic leaps in tress,
What is the size of the cerebellum?
The cerebellum is relative tiny during birth. However, it quickly develops in the first six years of our lives to reach its original size. During the first six years, it completes the wiring of basic and commonly repeated movements.
Describe the arrangement of the cerebellar cortex.
The cerebellar cortex is made up of three layers. The outer layer is made by superficial molecular cells. The second layers is a vey thin layer of purkinje cell and the third layer is a thick, dense layer of the granular cells.
The thickness of each layer is relative same throughout the whole cortex.
Where are and what are the three deep cerebellar nuclei?
Deep in the cerebellar white matter there are three deep cerebellar nuclei. They are called the lateral(dentate nucleus), interposed and medial nucleus.
What is the role of the purkinje cells in the cerebellar cortex?
They are the output cells of the cerebellum. They project to the deep cerebellar nuclei.
What does the dentate nucleus project to?
The dentate nucleus projects to the thalamus which then projects to the cortex. It also projects to the brainstem and the spinal cord.
Where does the input to the cerebellum go to?
Most of it goes to the granular layers. These fibres that terminate in the granular layer are called mossy fibres. A smaller pathway from the inferior olive directly goes to the purkinje cells. The inferior olive is a timer which helps the cerebellum in maintaining timely order for the movements. It fires 10 AP per second.
How many granule cells are there in the cerebellum?
The granule cells of the cerebellum consists of 70% of all neurons in the CNS.
What is a folium and its role?
A folium is a crinkle on the surface of the cerebellum. There are about tens of thousands of folia in the human cerebellum. Each folium codes for a specific movement sequence such as grasping, chewing and swallowing. Since there are this high number of folia in humans, we can continue learning new movement sequence throughout our life.
How does the motor system work, in relation to the cerebellum?
The motor cortex sends Corticopontine fibres to the pons where they synapse and crossover to the opposite side of the cerebellum. It enters the cerebellum through the middle cerebellar peduncle. The cerebellum corrects the plan for better coordination and sends this information to the thalamus via the superior cerebellar peduncle. The thalamocortical fibres then relays this information to the motor cortex. The cerebellum connects to the brainstem and corrects the movement directly if it is already in progress.
What is the cell number ratio of cerebellum to cerebral cortex?
What is the most important source of information to the cerebellum about movement?
The most important source of information on movement is provided by receptors that detect stretching, contact or folding in the skin. Initially, it was thought to be from the join receptors and muscle stretch receptors.
What is the parts of the striatum and pallidum?
The striatum is made up of the caudate nucleus, putamen and accumbens nucleus. The pallidum is mainly made up of the globus pallidus. The sub pallium contains the striatum, pallidum and the preoptic nucleus.
What is the role of the striatum and the pallidum?
The striatum and pallidum are huge masses of grey matter buried by the cerebral cortex. They are part of the chain that regulates the form and style of movements. The pyramidal cells in the fifth layer of the cortex projects glutamergic fibres to the striatum, which in turn projects to the pallidum. The pallidum then projects to the midbrain and the thalamus. GABAergic neurons are used in the connection to the thalamus, as the pallidum works by inhibiting the thalamic output. The thalamus then projects to the cerebral cortex and changes the plan of the movement or the movement which is already in progress.
What is necessary for the striatum and pallidum chain to work properly?
Dopamine. The substantia nigra is a nucleus in the midbrain that sends dopaminergic neurons to the striatal-pallidum complex.
Interesting fact about the purkinje cell in the cerebellar cortex.
They have upto half a million synapses connected to their dendritic tree.
Their dendritic tree fans out in 2 d fashion.
The tree lie as at 90 degree angle to the long axis of the folium it is situated in.
What is so important about the striatum and pallidum?
They enable movement.
They might also be the structures that give rises to the emotion and social behaviours that are predetermined by evolution.
What are the common symptoms when the striatum and pallidum are damaged?
Difficulty initiating movement
Unwanted involuntary movement
What is the internal capsule?
A thick white fibre sheet that carries the fibres from the cortex to the brainstem, thalamus, and the spinal cord. The internal capsule has the putamen and the globus pallidus on one side, and the thalamus on the other side. The caudal extension of the internal capsule is the cerebral peduncle. Since it carries all fibres from the cortex, it can be devastating if damaged.
What is curare and how does it work?
Curare is a poison extracted from a plant used by some South American tribes. It paralyses the animal or target by blocking the acetylcholine receptors in the the neuromuscular junction. The poison is only active at the time of the short, so the meat can be consumed without any effect. Curare analogs are now used to relax muscles in various types of surgery, however the patient has to be assisted my mechanical respirator as the respiratory systems are also paralysed.
What is an alpha motor neuron?
A neuron that is connected to a skeletal muscle by which that specific muscle is innervated.
What is a motor unit?
The alpha motor neuron and all the muscle fibres it is connected. So stimulation of the motor neuron causes all the muscle fibres it is connected to contract.
Who described the motor neuron as the final common pathway?
How are reflexes initiated? What does the reflex do?
Reflexes are initiated by incoming stimuli that activates local interneurons. The reflexes make quick adjustments to muscle activity to maintain muscle stretch, to prevent stresses, imbalance and overload, and avoid damage.
What mostly evokes reflexes?
Muscle spindles, adjustable and very sensitive length detectors, and Golgi tendon organs(force detectors located in tendons that attach muscle to bone)
What happens when a muscle is stretched?
The muscle spindle receptors are activated which makes a mono synaptic connection with the alpha motor neuron supplying the muscle to increase the tone to adjust the new load. Small gamma motor neurons from the ventral horn of the spinal cord constantly adjusts the sensitivity of the muscle spindle to prevent constant reflexes. This stretch reflexes are often tested during neurological examinations to test for hypereflexia which is often related to a stroke.
What happens when muscle develops too much force?
The Golgi tendons are stimulated. They instantly make inhibitory synapses to the alpha motor neuron supplying that specific muscle cutting the load and returning the force levels to a safe and manageable levels.
What causes hypereflexia?
Reflexes are useful to the body to prevent damage, however can be counter productive when easily stimulated. Therefore, they are slightly suppressed until voluntary movement is initiated. These interneurons are damaged during spinal damage and this causes the person to easily react to stimuli.
What is the autonomic nervous system?
The autonomic nervous system is also known as the visceral nervous system as it supplies the internal organs, glands, and blood vessels compared to the voluntary nervous system. The autonomic nervous system gets its name because all the responses and controls are automated and is not at a conscious level. The system is divided into the sympathetic and parasympathetic nervous system
What is special about the nerves that supply the heart?
The nerves that supply the heart are both sympathetic and parasympathetic nerves. The parasympathetic nervous system is constantly slowing down the heart muscles. The sympathetic nerves fastens the heart beat. Therefore, their actions cancel out. If the nerves supplying the heart is cut, the heart will continue to beat at 110 beats per minute because it has an intrinsic pacemaker.
What is the difference between adrenaline or noradrenaline?
They both are very similar in structure and the effect they have on the body. However, the noradrenaline is used as a neurotransmitter and is produced in the locus coeruleus of the hindbrain. The adrenaline is produced in the adrenal medulla and is used as hormone and is released into the blood stream.
Where is the sympathetic and parasympathetic motor systems located?
The sympathetic region is found in the thoracic and upper lumbar spinal cord segments(T1 to L2). The parasympathetic region is found in the brainstem(cranial nerves 3,5,7,9,10) and the sacral region of the spinal cord.
How has the autonomic nervous system overcome the difficult in supplying to such huge area?
The autonomic neurons mostly do not activate the target themselves instead the activate ganglions which spread the effect to a wide area. This system is more useful in the sympathetic nervous system as the response to stress is always the same, therefore the ganglia is closer to the spinal cord and the ganglia spreads over a wide region. The parasympathetic system uses ganglion over a shorter region with targets that have supplementary functions. This is better than the somatic system which needs to connect to every single muscle separately.
What are the parts of the ganglionic system?
The preganglionic cell and the postganglionic cell. The preganglionic cell is the cell that innervates the ganglion and the post ganglionic cell is the cell in the ganglia. The preganglionic cells in both systems are cholinergic. But the sympathetic ganglions uses noradrenaline whilst parasympathetic ganglia continues to use acetylcholine.
What are the functions of the sympathetic nervous system?
It is the response system to any fight or flight situation. It rapidly mobilises key bodily functions, prepares the body for action by raising blood pressure, relaxing and opening airways, mobilising energy sources and quickly shutting down digestion. The sympathetic nervous system also releases adrenaline into the bloodstream that helps the body to sustain the effects of the sympathetic nervous system
What are the functions of the parasympathetic nervous system?
The parasympathetic nervous system is responsible for the day to day function. It can be said to have eat and digest control. It does not act on the limbs, therefore it is restricted to the organs and the glands of the head and trunk. It is also responsible for penile erection and bladder emptying.
What does the vagus nerve supply?
It supplies the larynx, esophagus, lungs, heart, stomach, and small and large intestine.
What does vagus mean?
What does the sacral output of the parasympathetic nervous system supply?
Sigmoid colon, rectum, bladder and genitalia.
What are the effects of the neurotransmitter used by the autonomic nervous system?
The neurotransmitters has a wide range of effects on the target cell because there are varying receptors that are coupled to different combinations of intercellular machinery. This causes the same neurotransmitter to have different effects in different cells. This is seen when noradrenaline causes the gut walls to relax whilst it causes guts sphincter to contract. This is due to different adrenergic receptors.
What is special about the neurons in the enteric nervous system?
Some of the neurons do not clearly fit into the known categories of sensory, motor or interneurons and instead they perform like two or even three of these functions.
What are the higher autonomic control centres?
There are centres for cardiovascular, respiratory, salivation, swallowing, digestion, peristalsis, defecation and urination. The hypothalamus also triggers behavioural responses such as aggression. Anger is associated with increase in blood pressure, heart rate and respiration rate.
What is the enteric nervous system?
A network of neurons embedded in the wall of the gut, which regulates and coordinates its activity. It contains around 200-600 million neurons in the human body. It controls the contractions, intestines and other digestive organs. It is functionally linked to the immune system by helping it defend invasions from the microorganisms in the gut.
The enteric nervous system uses about 20 different transmitters, mainly GABA, VIP(vasoactive intestinal polypeptide), nitric oxide , acetylcholine and serotonin.
What is Hirschsprung disease?
Absence of parasympathetic innervation to part of the sigmoid colon, that makes it impossible to defecate. Treatment involves removal of the uninnervated part and the remaining sigmoid colon learns to defecate.
Explain the neuroendocrine system
The pituitary glands is the master gland of the endocrine system. It is under the control of the hypothalamus. There are two systems in the hypothalamus that control the pituitary gland. The anterior pituitary is controlled by parvicellular(small) neurons, and the posterior pituitary is controlled by magnocellular(big) neurons.
Explain how the anterior pituitary system work
The parvicellular neurons have short axons, so they secrete hypophysiotropic hormones into a special blood vessel system. These hypophysiotropic hormones stimulate or inhibit the anterior pituitary to release follicle stimulating hormone, luteinizing hormone, adrenocorticotrophin hormone, thyroid stimulating hormone, growth hormone and lactin. These hormones have effect on growth, reproduction, and regulation of the body.
Explain how the posterior pituitary system works.
The magnocellular neurons in the paraventricular and supraoptic neurons in the hypothalamus produces oxytocin and vasopressin. This travels down along their axons and is released into the bloodstream in the posterior pituitary.