1. What is the basic organization of a nervous system?
Answer: The nervous system is a complex network of specialized cells that coordinate the body's activities. It is organized into two main divisions: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
1. Central Nervous System (CNS):
Brain: The control center, responsible for processing information, thought, memory, and emotions. It includes the cerebrum, cerebellum, and brainstem. Spinal Cord: A long, tubular structure that connects the brain to the PNS. It carries sensory information to the brain and motor commands from the brain. It also mediates reflexes.
2. Peripheral Nervous System (PNS):
Consists of all the nerves outside the CNS. Somatic Nervous System: Controls voluntary movements (skeletal muscles) and carries sensory information. Autonomic Nervous System: Controls involuntary functions (heart rate, digestion, respiration). It is further divided into:
Sympathetic Nervous System: Prepares the body for "fight or flight" responses. Parasympathetic Nervous System: Promotes "rest and digest" responses.
3. Cellular Organization:
Neurons: The functional units that transmit electrical impulses. Neuroglial Cells: Support, protect, and nourish neurons. They include astrocytes, oligodendrocytes, microglia, and ependymal cells in the CNS, and Schwann cells and satellite cells in the PNS.
In summary, the nervous system is organized hierarchically, from the CNS to the PNS, with specialized cells for transmission and support. This organization allows for rapid communication and coordination of body functions.
2. Describe the structure of a neuron.
Answer: A neuron (nerve cell) is the structural and functional unit of the nervous system. It is specialized to receive, process, and transmit information.
Structure:
1. Cell Body (Soma): Contains the nucleus, cytoplasm, mitochondria, and other organelles. It is the metabolic center of the neuron.
2. Dendrites: Short, branched extensions that receive signals from other neurons and conduct impulses toward the cell body.
3. Axon: A single, long extension that conducts impulses away from the cell body. It can be very long (up to 1 meter). The axon hillock is the region where the axon joins the cell body.
4. Axon Terminals (Synaptic Knobs): Branched endings of the axon that form synapses with other neurons or effectors. They contain synaptic vesicles with neurotransmitters.
5. Myelin Sheath: A fatty insulating layer around some axons, formed by Schwann cells (PNS) or oligodendrocytes (CNS). It speeds up impulse conduction.
6. Nodes of Ranvier: Gaps in the myelin sheath where the axon membrane is exposed. They allow saltatory conduction.
Types of Neurons:
Sensory (Afferent): Carry impulses from receptors to CNS. Motor (Efferent): Carry impulses from CNS to effectors. Interneurons: Connect sensory and motor neurons within the CNS.
In summary, the neuron is a highly specialized cell with distinct regions for receiving, integrating, and transmitting information.
3. Describe the three types of neurons and write their functions.
Answer: Neurons are classified into three types based on their function and the direction of impulse transmission.
1. Sensory Neurons (Afferent Neurons):
Structure: Have a cell body in the dorsal root ganglion of the spinal nerve. They have a long dendrite that extends to the sensory receptor and a short axon that enters the spinal cord. Function: Transmit impulses from sensory receptors (e.g., skin, muscles, organs) to the central nervous system (CNS). They inform the brain and spinal cord about the external and internal environment.
2. Motor Neurons (Efferent Neurons):
Structure: Have a cell body in the ventral horn of the spinal cord or in the brainstem. They have a long axon that extends to the effector (muscle or gland). Function: Transmit impulses from the CNS to effectors. They cause muscles to contract or glands to secrete, producing a response.
3. Interneurons (Association Neurons):
Structure: Located entirely within the CNS (brain and spinal cord). They have many dendrites and axons, forming complex networks. Function: Connect sensory and motor neurons. They process and integrate information. They are involved in reflexes, learning, and memory.
In summary, sensory neurons carry information in, motor neurons carry commands out, and interneurons process the information
in between.
4. Describe the mechanism of synaptic transmission.
Answer: Synaptic transmission is the process by which a nerve impulse is transmitted from one neuron to another across a synapse.
Steps:
1. Arrival of Action Potential: The action potential arrives at the presynaptic axon terminal.
2. Calcium Influx: Voltage-gated calcium channels open, allowing Ca²⁺ to enter the presynaptic terminal.
3. Neurotransmitter Release: The influx of Ca²⁺ causes synaptic vesicles to fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft by exocytosis.
4. Receptor Binding: Neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane.
5. Postsynaptic Potential: This binding opens ion channels on the postsynaptic membrane, causing a change in its membrane potential (excitatory or inhibitory postsynaptic potential).
6. Termination: Neurotransmitters are removed from the cleft by reuptake, enzymatic degradation, or diffusion.
Types of Synapses:
Electrical Synapses: Direct flow of ions through gap junctions (rare in mammals). Chemical Synapses: Use neurotransmitters (most common).
In summary, synaptic transmission is a complex process that allows for communication between neurons and the integration of signals in the nervous system.
5. Write the classification of neurotransmitters.
Answer: Neurotransmitters are chemical messengers that transmit signals across synapses. They can be classified based on their chemical structure and function.
1. Based on Chemical Structure:
Acetylcholine: A small molecule. Involved in muscle contraction, memory, and arousal. Biogenic Amines: Derived from amino acids.
Catecholamines: Dopamine, norepinephrine, epinephrine. Indolamines: Serotonin. Histamine.
Amino Acids: GABA (inhibitory), glycine (inhibitory), glutamate (excitatory), aspartate (excitatory). Peptides: Endorphins, enkephalins, substance P, vasopressin, oxytocin. Gases: Nitric oxide, carbon monoxide.
2. Based on Function:
Excitatory: Depolarize the postsynaptic membrane (e.g., glutamate, acetylcholine). Inhibitory: Hyperpolarize the postsynaptic membrane (e.g., GABA, glycine). Modulatory: Modify the response of the postsynaptic neuron (e.g., dopamine, serotonin).
In summary, neurotransmitters are a diverse group of chemicals that play crucial roles in nervous system function. Their classification helps in understanding their roles in health and disease.
6. Describe the human brain.
Answer:
The human brain is the central organ of the nervous system, responsible for controlling all body functions, processing information, and generating thoughts and emotions. It is protected by the skull and meninges.
Major Parts:
1. Cerebrum: The largest part. Divided into two hemispheres (left and right) by the corpus callosum. It is the center of intelligence, memory, language, and voluntary movement. It has four lobes: frontal, parietal, temporal, and occipital.
2. Cerebellum: Located below the cerebrum. It coordinates voluntary movements, balance, and posture. It receives input from sensory systems and the cerebrum.
3. Brainstem: Connects the brain to the spinal cord. It includes:
Midbrain: Controls eye movement and auditory reflexes. Pons: Relays signals between the cerebrum and cerebellum; involved in sleep and arousal. Medulla Oblongata: Controls vital involuntary functions (breathing, heart rate, blood pressure).
4. Diencephalon:
Thalamus: Relay center for sensory information. Hypothalamus: Controls body temperature, hunger, thirst, and hormone secretion.
5. Limbic System: Includes amygdala, hippocampus, and other structures. Involved in emotions, memory, and motivation.
In summary, the human brain is a highly complex organ with specialized regions for different functions, working together to control the body and mind.
7. Describe the structure of spinal cord with diagram.
Answer: The spinal cord is a long, cylindrical structure that extends from the medulla oblongata down to the lower back. It is part of the
central nervous system and is protected by the vertebral column and meninges.
External Structure:
It is about 45 cm long in adults. It has two enlargements: cervical and lumbar, which supply nerves to the limbs. It ends in a tapered region called the conus medullaris. The cauda equina is a bundle of spinal nerves that extend below the spinal cord.
Internal Structure:
Gray Matter: Inner, butterfly-shaped region. Contains cell bodies, dendrites, and unmyelinated axons. It is divided into horns:
Dorsal Horn: Receives sensory input. Ventral Horn: Contains motor neurons. Lateral Horn: Contains autonomic neurons.
White Matter: Outer region. Contains myelinated axons organized into tracts.
Ascending Tracts: Carry sensory information to the brain. Descending Tracts: Carry motor commands from the brain.
Diagram Description: (A cross-section of the spinal cord showing the gray matter in a butterfly shape, surrounded by white matter, with dorsal and ventral roots and horns.)
Functions:
Conducts sensory and motor signals. Mediates reflexes.
In summary, the spinal cord is a vital structure with a highly organized internal arrangement for transmission of information and
reflexes.
8. Describe the somatic and autonomic nervous system.
Answer: The peripheral nervous system is divided into the somatic and autonomic nervous systems.
1. Somatic Nervous System:
Function: Controls voluntary movements and transmits sensory information. Components:
Sensory (Afferent) Neurons: Carry information from sensory receptors to the CNS. Motor (Efferent) Neurons: Carry commands from the CNS to skeletal muscles.
Neurotransmitter: Acetylcholine. Control: Under conscious control. Example: Moving your arm, feeling a touch.
2. Autonomic Nervous System (ANS):
Function: Controls involuntary functions (heart rate, digestion, respiration, pupil dilation). Components:
Sympathetic Division: Prepares the body for "fight or flight" (increases heart rate, dilates pupils, inhibits digestion). Parasympathetic Division: Promotes "rest and digest" (slows heart rate, constricts pupils, stimulates digestion).
Neurotransmitters: Acetylcholine, norepinephrine. Control: Involuntary. Example: Heartbeat, digestion.
In summary, the somatic nervous system controls voluntary actions, while the autonomic nervous system controls involuntary functions. Both are essential for survival.
9. Give an account of narcotic drugs.
Answer: Narcotic drugs are psychoactive compounds that act on the central nervous system to relieve pain, induce sleep, and produce euphoria. They are often derived from opium (opioids) or synthesized.
Types:
Natural Opioids: Morphine, codeine (from opium poppy). Semi-synthetic: Heroin (diacetylmorphine). Synthetic: Fentanyl, oxycodone, methadone.
Effects:
Therapeutic: Pain relief, cough suppression, diarrhea treatment. Recreational: Euphoria, relaxation, sedation.
Mechanism:
Bind to opioid receptors in the brain and spinal cord. Mimic endorphins, blocking pain signals. Activate the reward pathway (dopamine release), reinforcing use.
Risks:
Tolerance: Need for higher doses. Dependence: Physical and psychological addiction.
Withdrawal: Severe symptoms upon cessation. Overdose: Respiratory depression, coma, death. Infections: HIV, hepatitis from needle sharing.
In summary, narcotic drugs have legitimate medical uses but carry high risks of abuse, addiction, and overdose. They are controlled substances.
10. Describe the cause, symptoms and treatment of: a. Stroke, b. Headache, c. Meningitis, d. Tumour, e. Alzheimer disease
Answer:
a. Stroke:
Cause: Interruption of blood flow to the brain (ischemic or hemorrhagic). Symptoms: Sudden weakness/numbness (often one side), confusion, trouble speaking, vision problems, severe headache. Treatment: Clot-busting drugs (tPA), surgery, rehabilitation.
b. Headache:
Cause: Tension, migraine, sinusitis, medication overuse, or underlying conditions. Symptoms: Pain in the head, neck, or scalp. Treatment: Pain relievers, rest, hydration, treating underlying cause.
c. Meningitis:
Cause: Viral, bacterial, or fungal infection of the meninges. Symptoms: Severe headache, fever, stiff neck, nausea, sensitivity to light. Treatment: Antibiotics (bacterial), antivirals, antifungals, corticosteroids.
d. Tumour:
Cause: Abnormal cell growth in the brain (benign or malignant). Symptoms: Headaches, seizures, vision/hearing problems, cognitive changes. Treatment: Surgery, radiation, chemotherapy.
e. Alzheimer's Disease:
Cause: Neurodegenerative disease; amyloid plaques and tau tangles. Symptoms: Memory loss, confusion, difficulty with language, mood changes. Treatment: No cure; medications to manage symptoms (cholinesterase inhibitors, memantine).
11. Explain the principles of the following diagnostic tests of nervous disorders: a. EEG, b. CT scan, c. MRI
Answer:
a. EEG (Electroencephalogram):
Principle: Records electrical activity of the brain using electrodes placed on the scalp. Use: Diagnoses epilepsy, sleep disorders, brain tumors, and encephalitis. Procedure: Non-invasive, painless.
b. CT Scan (Computed Tomography):
Principle: Uses X-rays and computer processing to create cross-sectional images of the brain. Use: Detects tumors, bleeding, stroke, and skull fractures. Procedure: Painless, involves radiation exposure.
c. MRI (Magnetic Resonance Imaging):
Principle: Uses strong magnetic fields and radio waves to create detailed images of soft tissues. Use: Detects tumors, stroke, multiple sclerosis, and spinal cord injuries. Procedure: Non-invasive, no radiation, but noisy and requires staying still.
12. Describe the way how pain medicines can reduce or numb pain in the human body.
Answer: Pain medicines (analgesics) work by interfering with the transmission or perception of pain signals in the nervous system.
1. Non-Opioid Analgesics (NSAIDs):
Mechanism: Inhibit cyclooxygenase (COX) enzymes, reducing the production of prostaglandins, which sensitize pain receptors. Examples: Aspirin, ibuprofen, naproxen. Use: Mild to moderate pain, inflammation.
2. Opioid Analgesics:
Mechanism: Bind to opioid receptors in the brain and spinal cord, blocking pain signals and altering the perception of pain. Examples: Morphine, codeine, fentanyl. Use: Severe pain.
3. Local Anesthetics:
Mechanism: Block sodium channels in nerve membranes, preventing the generation and conduction of nerve impulses. Examples: Lidocaine, novocaine. Use: Numbing a specific area for procedures.
In summary, pain medicines act at different levels of the nervous system to reduce or numb pain, providing relief for various conditions.
