Anatomy and pattern recognition of the central nervous systemnormal radiographic appearances and pathology Flashcards
What are the functions of the nervous system?
Sensory input- gathers info, sound, glucose levels. This involves gathering information from sensory receptors that monitor changes both inside and outside the body.For example, sensory neurons detect stimuli like temperature, light, and sound, and send this information to the central nervous system (CNS) for processing1.
Integration- Once the sensory input reaches the CNS, it is processed and interpreted. The CNS, which includes the brain and spinal cord, analyzes the sensory data and decides on an appropriate response.This step is crucial for making sense of the information and determining the necessary action2.
Motor output- response, sends signals to organs. After integration, the nervous system sends signals from the CNS to effector organs, such as muscles and glands, to initiate a response. This could be anything from moving a muscle to secreting a hormone.Motor neurons carry these signals to the target organs to execute the response3.
These functions work together seamlessly to help the body respond to its environment and maintain homeostasis
Homeostasis regulation- maintain internal stability eg temp.Homeostasis is the process by which biological systems maintain a stable internal environment despite changes in external conditions. This stability is crucial for the survival and proper functioning of organisms. Here are the key aspects of homeostasis:
Definition: Homeostasis refers to the self-regulating processes that organisms use to maintain internal stability.This includes regulating temperature, pH levels, glucose concentration, and other vital conditions1.
Mechanisms: Homeostasis involves feedback mechanisms, primarily negative feedback, which counteracts changes to bring the system back to its set point.For example, if body temperature rises, mechanisms like sweating and increased blood flow to the skin help cool the body down2.
Examples:
Body Temperature: The human body maintains a temperature around 37°C (98.6°F).If it gets too hot, the body sweats to cool down; if it gets too cold, the body shivers to generate heat1.
Blood Glucose Levels: The pancreas regulates blood sugar by releasing insulin when glucose levels are high and glucagon when they are low2.
Water Balance: The kidneys regulate water balance by adjusting the concentration of urine based on the body’s hydration levels2.
Homeostasis ensures that the body’s internal environment remains consistent, allowing cells and organs to function optimally
Mental activities
Reflex actions
Provides an immediate response when required.
Provide a slower, long term response when required through stimulation of endocrine system and release of hormones
The human nervous system is incredibly complex and performs several vital functions to keep the body operating smoothly. Here are the main functions:
Sensory Input: The nervous system gathers information from sensory receptors that detect changes both inside and outside the body.This includes sensations like touch, temperature, pain, and sound1.
Integration: The central nervous system (CNS), which includes the brain and spinal cord, processes and interprets sensory input.It integrates this information to make decisions and coordinate appropriate responses2.
Motor Output: After processing the sensory input, the nervous system sends signals to muscles and glands to elicit responses.This could involve moving a muscle, secreting a hormone, or other actions3.
Homeostasis Regulation: The nervous system helps maintain homeostasis by regulating bodily functions such as heart rate, blood pressure, digestion, and body temperature4.
Mental Activities: It is responsible for higher functions such as thinking, memory, learning, and emotions.The brain processes complex information and enables cognitive functions5.
Reflex Actions: The nervous system controls reflexes, which are automatic responses to certain stimuli.These reflexes help protect the body from harm, such as pulling your hand away from a hot surface6.
These functions are carried out by the central nervous system (CNS) and the peripheral nervous system (PNS), working together to ensure the body responds appropriately to various stimuli and maintains internal balance
Overview of the organisation of the nervous system
Central nervous system- brain and spinal cord
Peripheral nervous system- Peripheral is all the nerves outside of the CNS – divided into sensory and motor.
Sensory- – carries information from sensory receprors to the CNS
Motor- transmits signals from the CNS t effector rogans like the muscles
Somatic- voluntary movements e.g. walking, talking,
Autonomic nervous system- involuntary like heart rate, digestion and respiratory rate.
Further divided into sympathetic and parasympathetic.
Sympathetic- prepares body for flight or fight response (increases heart rate, releases energy).
parasympathetic- – rest and digest activities – slows heart raterelaxing sphincter muscles
Principal cells – glia – provide support and protection for neurons. Form myelin and maintain homeostasis
Neuron – primary cells of the CNS that transmit electrical and chemical signals.
What is myelin?
It is a fatty sheath that wraps around the axons of neurons (the bit of the neuron that conducts electrical impulses away from the neuron cells body)
Composed of lipids and proteins
Insulates the axons and increases the speed of electrical impulses as they travel along nerve cells.
Produced by Glia cells
CNS – oligodendrocytes
PNS – Schwann cells
Helps transmit electrical impulses. helps with all responses.
What are neuron’s?
Sometimes called a ‘nerve cell’
Is the fundamental structural unit of the nervous system which transmits information throughout the body.
Types of neurons
Sensory neurons
Motor neurons
Interneurons
Special characteristics
Longevity
Amitotic
High metabolic rate
What is longevity in neurons?
Neurons can live and function for a lifetime.Unlike many other cells in the body, which are regularly replaced, neurons are generally not replaced once they are lost1.
What is amitotic in neurons?
Most neurons do not undergo mitosis after they are fully developed. This means they do not divide and reproduce.Once a neuron is damaged or dies, it is typically not replaced2.
What is High Metabolic Rate?
Neurons have an exceptionally high metabolic rate. They require a continuous supply of oxygen and glucose to function properly.This high demand for energy is due to their role in transmitting electrical impulses and maintaining the ionic gradients necessary for signal transmission.
What is grey and white matter?
Grey Matter – collections of nerve cell bodies and their dendrites
Nuclei
Ganglia
White matter – myelinated fibres – tracts conveying nerve impulses from generation site to target
Membrane potential
Difference of charges across the plasma membrane. refers to the difference in electrical charge across a cell’s plasma membrane.This difference is due to the unequal distribution of ions inside and outside the cell1.
Resting potential is the membrane potential of a neuron when it is not actively transmitting a signal. In this state, the inside of the neuron is negatively charged relative to the outside.Typically, the resting potential is around -70mV2.
Difference of Charges: At rest, there are more positive ions (Na⁺) outside the cell and more negative ions (K⁺) inside the cell.This creates a negative charge inside the cell and a positive charge outside2.
Resting cells are (-) inside and (+) outside
Large amounts of Na+ outside the cell and K+ inside
Action potential/impulse. Anaction potentialis a rapid change in membrane potential that travels along the axon of a neuron. It is the electrical impulse that neurons use to communicate.
Rapid Reversals: During an action potential, the charges across the membrane reverse rapidly.The inside of the cell becomes positive relative to the outside3.
Ion Exchange: This reversal is caused by the movement of ions across the neuron’s membrane.Sodium ions (Na⁺) rush into the cell, followed by potassium ions (K⁺) rushing out3.
Rapid reversals in charges across the plasma membrane
Caused by the exchange of ions across the membrane of the neuron
Threshold level (-55mV) needed to stimulate neurons ALL-OR-NONE principle. Thethreshold levelis the critical level to which the membrane potential must be depolarized to initiate an action potential. For most neurons, this threshold is around -55mV.
All-or-None Principle
Theall-or-none principlestates that once the threshold level is reached, an action potential will fire completely. If the threshold is not reached, no action potential will occur. This means that action potentials are always the same size; they do not vary in strength
How are impulses terminated? – termination of neurotransmitter effects
Degradation of neurotransmitter by enzyme
Reuptake of neurotransmitter
Diffusion of neurotransmitter from synapse
Synapse: Excitatory or Inhibitory
Excitatory Synapses and Excitatory Postsynaptic Potentials (EPSPs)- : Increase the likelihood of an action potential by depolarizing the postsynaptic membrane.
Inhibitory Synapses and Inhibitory Postsynaptic Potentials (IPSPs). Decrease the likelihood of an action potential by hyperpolarizing the postsynaptic membrane.
These processes are essential for the complex regulation of neural activity, allowing the nervous system to integrate and respond to a vast array of signals.
Anaction potentialis a rapid and temporary change in the electrical membrane potential of a neuron or muscle cell. This change allows the cell to transmit an electrical signal along its membrane. Here’s a detailed breakdown:
What is meninges?
Cover and protect Central Nervous System (CNS)
Contains Cerebrospinal fluid (CSF)
Protect blood vessels
Dura mater – 2 layers of fibrous tissue mostly attached, fibrous outer attached to skull and an inner enclosing the Central Nervous System
Arachnoid mater– separated from the dural by the sub-dural space and covers the pia mater. Connects to this by web like extensions forming the sub-arachnoid space. This is a large space filled with CSF and blood vesssels
Pia mater – innermost layer attaches to the brain
What is Meninges – Dura mater ?
Dura mater
Separation of layers forms:
Dural partition of brain:
Falx cerebri, tentorium cerebelli, Falx cerebelli.
Intracranial venous structures (sinuses) Superior sagittal sinus, inferior sagittal sinus, confluence of sinuses, straight sinus, transverse sinus
Extradural space between periosteal (outer) layer and bone of skull
Subdural space between meningeal (inner) layer and arachnoid mater.
Spinal cord
Extends as a loose sheath from foramen magnum to the 2nd sacral vertebra.
What is Meninges – Arachnoid mater?
Arachnoid mater
Passes over the convolutions of the brain.
Merges with the dura mater to at the 2nd sacral vertebra.
Arachnoid mater separated from :
Dura mater by subdural space
Pia mater by subarachnoid space.
What is Meninges – Pia mater?
Pia mater
Connective tissue
Adheres to brain covering dipping into fissures
Continues beyond spinal cord with filum terminale
Sheaths (covers) blood vessels
Fuses to periosteum of the coccyx with dura mater.
What are ventricles (brain relation)?
Irregular shaped cavities located within the brain.
Protects brain, acts as a shock absorbent.
Contain cerebrospinal fluid (CSF)
CSF: Suspends brain cells – provides buoyancy and a fluid environment for biochemical activity. Thus protects and maintains viability.
CSF is like plasma with less protein and a different electrolyte composition. It is essential for brain function, e.g. very sensitive to pH, affecting breathing and perfusion of blood.
Consist of defined aspects:
Left and right lateral ventricles
Third ventricle
Fourth ventricle
What does the ventricle system consist of?
The ventricular system of the brain consists of four interconnected cavities filled with cerebrospinal fluid (CSF). These ventricles play a crucial role in protecting the brain, providing nutrients, and removing waste. Here’s a breakdown of each component:
Left and Right Lateral Ventricles
Location: These are the largest ventricles and are located within each hemisphere of the cerebrum.
Structure: Each lateral ventricle has three extensions called horns: the frontal (anterior) horn, the occipital (posterior) horn, and the temporal (inferior) horn1.
Function: They produce and contain CSF, which flows through the interventricular foramina (foramina of Monro) into the third ventricle2.
Third Ventricle
Location: Situated in the midline of the brain, between the two halves of the thalamus.
Structure: It is a narrow, slit-like cavity that connects to the lateral ventricles via the foramina of Monro and to the fourth ventricle via the cerebral aqueduct (aqueduct of Sylvius)3.
Function: The third ventricle also produces CSF and serves as a pathway for its flow from the lateral ventricles to the fourth ventricle.
Fourth Ventricle
Location: Located between the pons and the medulla oblongata, and anterior to the cerebellum.
Structure: It has a characteristic diamond shape and connects to the central canal of the spinal cord and the subarachnoid space via three openings: the median aperture (foramen of Magendie) and two lateral apertures (foramina of Luschka)4.
Function: The fourth ventricle continues the flow of CSF from the third ventricle and distributes it around the brain and spinal cord4.
These ventricles are essential for the production, circulation, and removal of cerebrospinal fluid, which cushions the brain and spinal cord, maintains chemical stability, and removes waste products.
