nervous system Flashcards
What is the role of the nervous system?
NS monitors internal & external environments, it processes information from both environments and directs body processes accordingly
What are the purpose of glial cells?
They act as messengers, responsible for maintaining an extracellular environment, supply nutrients, guiding neural development, improve speed of communication across the body, contain a concentration of neurotransmitters
What does the CNS consist of?
Brain and the spinal cord
What does the PNS consist of?
Neurones, spinal nerves & ganglia
Define the autonomic NS
Autonomic NS consists of the parasympathetic pathway & sympathetic pathway
Para-refers to the rest & digest state, this requires no conscious action, it regulates digestion & urine production, their fibres originate in the brain, have long preganglionic & short postganglionic fibres, and most of their ganglia are located within visceral organs e.g., bladder
uses ACH neurotransmitter
symp-known as fight/flight, speeds up HR,HB,BR & stimulates glucose release from liver
ganglia is found near the spinal cord, reduces para processes.
Has short preganglionic & long postganglionic fibres
Fibres originate from lumbar regions
Norepinephrine is main neurotransmitter involved
Define the somatic NS
The somatic consists of the voluntary skeletal muscles, deals with movements we make consciously
They have heavily myelinated neurons which release Ach at terminal, they work on skeletal muscles
Describe the structure and function of the meninges
Their role is to cover & protect CNS, BV’s and venous sinuses
Contains CSF
Forms some partitions of the skull
What are the 3 layers of the meninges?
Dura Mater- toughest and thickest layer, 2 fibrous layers periosteal attaches to internal skull surface & meningeal attaches to external brain covering.
They are fused in some areas, however they separate to enclose venous sinuses so they can drain blood from the brain into the jugular veins
Arachnoid Mater- forms a loose brain covering, separated from DM by serous cavity (has CSF), spider-like extensions extend from cavity space and secure AM to PM
Contains granulations to absorb CSF into venous blood of the sinus
Pia Mater-made of delicate connective tissue & has many tiny BV’s, the only meninge to cling to the brain, small arteries entering the brain carry sheaths of PM inward with them
Define the function of the Dura septa
Limits movement of the brain in the cranium
Describe the formation and function of the cerebral spinal fluid
It is produced by the choroid plexus & brain tissues
Choroid plexus of each ventricle produces CSF
CSF flows into & through subarachnoid space (between DM &AM)
CSF is absorbed by venous sinuses via arachnoid granulations
Function: provide nutrients e.g., glucose, remove waste/ metabolites e.g., urea, provide a stable environment & provide cushioning (protective measure)
CSF reduces brain mass by 97%, prevents brain from being crushed by it’s own weight.
CSF contains more Na+, Cl- & H+ than blood plasma, but less K+ and Ca2+
What is the Gyri?
They are the ridges of the brain & separated by the sulci. Gyri increase SA of the brain enabling greater cognitive processing
Consists of 2 types of gyrus: pre & postcentral
What is the function of precentral & postcentral gyrus?
Precentral- contains the primary motor cortex which controls voluntary movement
Postcentral-Contains primary somatosensory cortex which processes touch and other body sensations
What is the sulci?
They separate the hemispheres into lobes allowing them to be separated and easily identified. They increase the SA of the brain, allowing more neural connections in the brain
Has 3 types central sulcus, parieto-occipital sulcus & lateral sulcus
Describe the 3 main sulci
Central- separates frontal & parietal lobes from each other, pre & postcentral gyrus border the central sulci
Parieto-occipital- seperates the parietla & occipital lobe from each other
Lateral sulcus-outlines the temporal lobe, separates it from frontal & parietal. Insula is buried deep within lateral sulcus. The insula is covered by portions of the temporal, frontal & parietal lobes
Describe the structure and function of the grey matter
- has short non-myleinated neurons & neuron cell bodies
- it contains glial cells, involved in the protection & support of neurones, waste removal & homeostasis
- It contains BV’s, but no long-fibres tracts
Describe the structure and function of the white matter
-Contains myleinated axons as well as fibre tracts
- has fatty mylein which give white colour
- white matter connects areas of the brain allowing communication, it uses motor & sensory pathways
Name all the lobes of the brain
-Frontal lobe
- Temporal lobe
- Parietal lobe
- Occipital lobe
- insula
- cerebellum
Describe the function of the insula
Involved in emotions & empathy, consciousness as well as gustation (sense of taste) and error detection in homeostasis
Describe the function of the temporal lobe
Contains the broca & wernickes area. It has the auditory complex involved in processing sounds, speech & song.
Broca involved in speech production
Wernicke involved in language analysis
Describe the function of the frontal lobe
Involved in information processing, decision making, emotions, smell & self-control. It contains the motor cortex which controls voluntary movements
Describe the function of the cerebellum
The back area of the brain involved in balance, posture and movement
Describe the function of the occipital lobe
Is involved in visual recognition, vision & contains visual cortex allowing us to process colours & shapes
Describe the function of the parietal lobe
It contains the sensory cortex, involved in pain, temperature & touch
They receive input from the skin from propioreceptors
What is a cortice?
The outermost layer of an organ
Describe the brainstem
Contains the pons, midbrain & medulla
- contains ascending & descending nerve tracts and so information flows in both directions
- involved in sleep, pain, regulates cardio/resp system
- has a reticular formation
Describe and explain the structure & function of the parasympathetic pathway in the ANS
Para-refers to the rest & digest state, this requires no conscious action, it regulates digestion & urine production, their fibres originate in the brain, have long preganglionic & short postganglionic fibres, and most of their ganglia are located within visceral organs e.g., bladder
Acetylcholine is released at pre & postganglionic
Describe and explain the structure & function of the sympathetic pathway in the ANS
symp-known as fight/flight, speeds up HR,HB,BR & stimulates glucose release from liver
ganglia is found near the spinal cord, reduces para processes.
Has short preganglionic & long postganglionic fibres
Fibres originate from lumbar regions
Norepinephrine is main neurotransmitter involved
Describe the effect of the parasympathetic & sympathetic NS on the following organs: eye, heart, lungs, Liver, sweat glands & salivary glands
Eye-constricts pupil (PSN), stimulates dilator muscle, widens pupil (SNS)
Heart-Decreases HR (PNS), increases HR and force of heartbeat (SNS)
Lungs- Constricts bronchioles (PNS), dilates bronchioles (SNS)
Liver- increases glucose uptake from blood (PNS), Stimulates release of glucose to blood (SNS)
Sweat glands-no effect (PNS), Stimulates sweat glands (SNS)
salivary glands-stimulates watery saliva production (PNS), stimulates production of thick viscous saliva (SNS)
Describe the structure and function of neuroglial cells
There are different types of glial cells—astrocytes, oligodendrocytes, microglia, ependymal cells, Schwann cells, and satellite cells—each have specialized roles
Function-
Supporting Neurons: Glial cells provide structural support, maintain the extracellular environment, and help supply nutrients and oxygen to neurons.
Insulation: Myelinating glial cells (oligodendrocytes in the CNS, Schwann cells in the PNS) create myelin sheaths that insulate axons, ensuring faster signal transmission.
Homeostasis: Glial cells maintain the balance of ions (such as potassium, calcium, and sodium) and neurotransmitters in the extracellular space, ensuring the proper functioning of neurons.
Immune Defense: Microglia act as immune cells in the CNS, responding to injury and infection, while other glial cells help maintain the integrity of the blood-brain barrier.
Repair and Regeneration: In the PNS, Schwann cells support nerve regeneration after injury. In the CNS, the regenerative capacity of glial cells is more limited, though some glial cells, like astrocytes, play a role in scar formation after injury
Explain what a sensory or motor homunculus is and describe the relationship between this concept and the primary somatosensory cortex and the primary motor cortex.
There is a contralateral representation, meaning the right side of the brain controls the left side of the body and vice versa.
In summary, the sensory homunculus is an exaggerated representation of how sensory input from different body parts is mapped onto the somatosensory cortex, while the motor homunculus shows how motor control of body parts is mapped onto the motor cortex. Both maps reflect the relative importance and complexity of sensory perception and motor control for different body regions.
What is the choroid plexus?
A cluster of capillaries enclosed via the PM then by ependymal cells (type of glial cell), each ventricle produces CSF
Define somatotopy
point-for-point correspondence of an area of the body to a specific point on the central nervous system.
Describe the brain stems control on the cardiac output
The medulla in the brainstem controls heart rate, blood pressure & blood vessel diameter
The cardio control centre consists of 2 centres: cardioinhibitory and cardio acceleratory
Cardio AC: signals released from the medulla via the sympathetic pathway releasing norepinephrine which increases HR & CO
Cardio INH: Signals are sent via parasympathetic pathway NS via the vagus nerve which releases ACH to decrease HR & CO
It uses baroreceptors and chemoreceptors to regulate heart rate to maintain homeostasis
Describe the brain stems control on the respiratory system
The brainstem organizes automatic & involuntary mechanisms associated with breathing to maintain homeostasis. The somatic can be engaged to involve voluntary control in breathing e.g., in response to emotional situations
Breathing is regulated by the medulla oblongata & pons which control rhythm & depth of breathing
Chemoreceptors are involved to monitor CO2, O2 & pH in blood concentration allowing breathing to be adjusted if needed
Autonomic regulation through the sympathetic and parasympathetic nervous systems helps fine-tune breathing in response to physiological demands, such as exercise, stress, or rest.
Reflexes like the Hering-Breuer reflex protect the lungs from over-expansion, while other reflexes help expel irritants or foreign bodies from the respiratory tract.
What are the 3 main nuclei’s involved in control of respiratory system
Pontine nuclei
Ventral respiratory group
Dorsal respiratory group
(input also received from solitary nucleus
What are the 4 main nuclei’s involved in control of cardiac output
Pressor area- The pressor area is responsible for activating the sympathetic nervous system (SNS) in response to certain stimuli, such as low blood pressure, stress, or exercise. It sends excitatory signals to sympathetic preganglionic neurons, which then release norepinephrine (NE) at various target tissues, including the heart and blood vessels. The pressor area’s function is to elevate cardiac output and blood pressure to ensure that the body’s organs receive sufficient blood supply during times of stress, exertion, or in response to hypotension.
Solitary nucleus- receives sensory input from baroreceptors and chemoreceptors. It plays a critical role in the reflex regulation of heart rate and blood pressure.
Depressor area- he depressor area primarily functions to decrease cardiac output and lower blood pressure by reducing sympathetic tone, leading to slower heart rate, reduced myocardial contractility, and vasodilation
Nucleus ambiguous-It regulates heart rate by reducing the heart rate via the vagus nerve
