Tag: Brain

Introduction

Animals have sophisticated nervous systems. It is a vital system that controls all of our body’s voluntary and involuntary movements.  The nervous system controls all complicated functions, including reading, remembering, feeling emotions, and logical thought.  The brain, spinal cord, and nerve network are all parts of the nervous system.

Together, these organs carry out the complex functions of the nervous system.

Nervous System Classification

The nervous system is classified into 3 types i.e the Central nervous system(CNS), the Autonomic nervous system(ANS), and the Peripheral Nervous System (PNS).

Central nervous system(CNS)

• The spinal cord and brain together make up the CNS. 
• The brain is covered by a fluid known as a Cerebrospinal fluid(CSF).
• Three membranes—the dura mater, arachnoid, and pia mater—cover the brain.
• Humans are made up of the forebrain, midbrain, and hindbrain.
• The forebrain is made up of the diencephalon and cerebrum and is further divided into the dorsal thalamus and ventral hypothalamus.
• The cerebrum is in charge of our motivation, reasoning, imagination, memory, thinking, and consciousness.
• The midbrain is made up of four circular structures called the cerebral aqueduct and corpora quadrigemina.
• The hindbrain is made up of the cerebellum, medulla oblongata, and pons.
• All voluntary motions and body equilibrium are controlled by the cerebellum, whereas the pons regulates breathing and the sleep cycle.
• The medulla oblongata regulates breathing, circulation, gastric secretions, vomiting, and salivation.
• The spinal cord is a cylindrical structure that resides in the neural canal of the vertebral column.
• The spinal cord is the location where all the nerves join and the information is sent to the brain.

Autonomic nervous system(ANS)

• ANS is known as the Autonomic Nervous system.
• It regulates the body’s internal organs’ involuntary functions.
• The sympathetic and parasympathetic nervous systems are the two types of ANS.

Peripheral Nervous System (PNS)

• The PNS is made up of nerves that emerge from the spinal cord and brain.
• The term “cranial nerves” refers to nerves that are emerging from the brain.
• Spinal nerves are nerves that arise from the spinal cord.

Parts of the nervous system

Neurons are the structural and functional components of the nervous system. Neurons are typically referred to as nerve cells. It is the longest cell in the human body and sends electrical impulses as messages. 

Following are the parts of a neuron.

• Cyton: The cell body is the main component of the neuron. The cyton contains cell organelles, a nucleus, and cytoplasm.
• Dendrites: These cytoplasmic extensions that protrude from the cell body are numerous and highly branched. They carry electric impulses both inside and outside of the cell body.
• Axon: It emerges from the cyton as a solitary, unbranched cylindrical projection. A myelin sheath protects the axon. It transports impulses away from the cyton.

Functions of the nervous system

• The network of neurons is in charge of message reception and transmission, which in turn controls and coordinates the various bodily parts.
• The cerebrum is in charge of our intelligence, thinking, consciousness, memory, imagination, reasoning, and willpower.
• The nervous system also controls voluntary movement and body balance. The cerebellum is in charge of this activity.
• The spinal cord is involved in the reflex action and helps in quick response during dangerous situations.
• The Nervous system of the body is responsible for controlling all automatic reactions to peripheral nerve stimulation such as breathing, stomach secretion, vomiting, etc.

Types of nerves

Classification of nerves is based on function, structure, and myelin sheath.

Classification based on function

• Afferent or  Sensory  Neurons: These nerves perform the function of carrying impulses to the Central Nervous system from the various sense organs such as eyes, nose, skin, etc.

• Efferent or Motor Neurons: These nerves perform the function of carrying impulses from the Central Nervous system to various effector organs such as muscles, organs, etc.
• Interneurons or Association Neurons: This neuron help in transferring impulses between the Sensory and Motor neurons.

Classification based on the structure

• Unipolar Neurons: In these neurons, the cell body gives rise to only a single nerve process that performs the function of both axon and dendron. These are seen in the spinal and cranial nerve ganglia.
• Bipolar Neurons: Here, two nerve processes are formed from the cell body. One of these becomes the axon and the other becomes the dendron. These are found in various sensory organs such as the nose, tongue, eye, etc.
• Multipolar Neurons: Multiple dendrons are generated from a single-cell body. These are the most common types of neurons found in the nervous system.

Classification based on the myelin sheath 

• Myelinated nerve fiber: A myelin sheath protects the axon 
• Non-myelinated nerve fiber: The nerve fiber here is not protected by the myelin sheath.

Summary

The human nervous system is the body’s most complicated network system. It is made up of the autonomic, peripheral, and central nervous systems. It enables us to carry out routine tasks, difficult activities, and bodily functions.  With the aid of a sophisticated network of nerves, the nervous system functions as a communication network that sends and receives signals from the brain and spinal cord to every area of the body. The nervous system is made up of neurons and based on their structures, functions, and whether or not myelin sheaths are present, neurons are further classified.

Frequently asked question

1. What is the Cerebrospinal fluid?
Ans: The brain’s ventricles (hollow spaces) are lined with tissue. This tissue produces cerebrospinal fluid. This fluid circulates around and inside the brain and spinal cord to nourish and protect them.

2. What signs of a weak neurological system?
Ans: Symptoms of disorders of the nervous system are-

• headaches that develop suddenly or persistently.
• tingling feeling or loss of sensation.
• loss of muscle strength or weakness.
• eyesight loss or double vision
• memory deterioration
• reduced mental capacity

3. Which components have a negative impact on the nervous system?
Ans: Following have a negative impact on the nervous system 

• Trauma (injuries), particularly spinal cord and head trauma.
• Issues that exist from birth (congenital).
• Mental health issues such as depression, psychosis, or anxiety disorders.
• Exposure to poisons like lead, arsenic, or carbon monoxide.

Introduction

The human body contains a variety of endocrine glands that secrete various hormones, each with a unique function. To maintain the body’s normal physiological state, each hormone must be present in sufficient amounts. Any variation in an endocrine gland’s hormone release obviously affects the body’s natural state of health. One adrenal gland is located above each kidney in a pair. Blood pressure, stress reactions, and body metabolism are all influenced by the adrenal hormones. Adrenal insufficiency is the term used to explain when the body produces less of these hormones than is necessary.

What is the Adrenal gland?

Adrenal glands are the triangular-shaped, small-sized glands lying on the top of each kidney. For this reason, they are also called the suprarenal glands. A cross-section of the adrenal gland shows two layers where the outer layer is called the cortex, and the inner layer is called the medulla.

The largest portion of the gland is the outer adrenal cortex. Zones glomerulosa, fasciculata, and reticularis make up its structure. At the center of the triangle, gland is the inner adrenal medulla. The cortex and medulla of the gland are shielded by an exterior capsule to maintain their endocrine activity.

For more help, you can Refer to Lesson 10 – Adolsence in life in Science Class 8 Lesson. Checkout the video for a better understanding

Hormones secreted

The cortex and medulla produce separate endocrine secretions. Different hormones with various roles are secreted by the adrenal cortex’s various zones.

Adrenal cortical hormones: Three distinct hormones are secreted by the adrenal cortex from its three layers.

1. Glucocorticoids: The zona fasciculata layer of the adrenal cortex secretes the main glucocorticoid hormone, cortisol. It is the body’s own natural steroid and is released in response to stress. The hormone cortisol regulates the body’s blood pressure, metabolism, and sleep-wake cycle. The body can better handle stress and emergency situations thanks to it as well. By encouraging its creation, cortisol also keeps the body’s levels of glucose stable.
2. Mineralocorticoids: The main mineralocorticoid released by the zona glomerulosa is aldosterone. Aldosterone’s primary job is to keep the body’s electrolyte and water balance in check. It works by telling the kidneys to remove potassium from the body and reabsorb sodium into the bloodstream.
3. Adrenal Androgens: The androgens secreted by the zona reticularis include testosterone and DHEA (Dehydroepiandrosterone), which are known as adrenal androgens. Male hormones called adrenal androgens are weak. Although females also release testosterone, the majority of it is a precursor that is transformed into estrogens in the ovaries.

Hormones of the adrenal medulla:

• Catecholamines are a broad term for adrenal medullary hormones. They contribute to the physiological effects of stress. The catecholamines are dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). 
• The stress-related blood pressure, heart rate, respiration, pupil dilation, and pale discoloration are brought on by the hormones adrenaline and norepinephrine. They are known as the flight and fear hormones for this reason.

Adrenocorticotropic hormone (ACTH), which is secreted by the pituitary gland, regulates the release of androgens and glucocorticoids from the adrenal glands. The hypothalamic secretions corticotropin-releasing hormone (CRH), antidiuretic hormone (ADH), and vasopressin regulate the pituitary’s release of ACTH.

Diseases related to insufficiency

The release of glucocorticoids, mineralocorticoids, and androgens can be impaired by damage to the cortical tissue or any malfunction. The condition is known as adrenal insufficiency. There could be a number of causes for this condition.

1. Primary adrenal insufficiency:

• It is also known as autoimmune adrenalitis or Addison’s disease. It happens as a result of disease in the cortical region of the adrenal glands. 
• It is characterised by diminished adrenal gland function. 
• It develops as a result of autoantibodies targeting the adrenocortical enzymes causing the self-destruction of adrenal tissues. 
• Other reasons include malignancies, infections with syphilis or tuberculosis, and adrenal haemorrhage.

2. Secondary adrenal insufficiency:

• It happens when the pituitary gland does not secrete enough ACTH to support adequate levels of adrenal hormone output. 
• Traumatic brain damage and panhypopituitarism cause this disease.

3. Tertiary adrenal insufficiency:

• This results from the hypothalamus’s insufficient secretion of corticotropin-releasing hormone (CRH). 
• Patients who undergo particular operations to treat Cushing’s syndrome have also reported experiencing it.

Compared to the other two kinds, primary adrenal insufficiency is more common. The medulla is largely unaffected, whereas the cortex is impaired. As a result, the production of aldosterone and cortisol decreases in those with this illness.

Symptoms:

• Fatigue and weakness
• Joint pains
• Hyperpigmentation
• Weight loss
• Salt cravings
• Low blood pressure and hypotension
• Abdominal pain
• Decreased body hair in women
• Decreased libido
• Low blood glucose 

The participants are examined for preexisting hyponatremia, hyperkalemia, and hypoglycemia as soon as symptoms appear. Adrenal insufficiency is established with blood tests, including those for ACTH, cortisol, renin, and aldosterone, and is then successfully treated. Hormone replacement therapy is a significant component of treatment.

Summary

Adrenal glands are the triangular-shaped, small-sized glands lying on the top of each kidney. The largest portion of the gland is the outer adrenal cortex. Catecholamines are a broad term for adrenal medullary hormones. They contribute to the physiological effects of stress. Primary adrenal insufficiency is also known as autoimmune adrenalitis or Addison’s disease. It happens as a result of disease in the cortical region of the adrenal glands.

FAQ’s

1. Define autoantibodies?
   Ans. Autoantibodies are proteins synthesised by one’s own immune system owing to the destruction of one’s self-tissues and organs. Due to autoantibodies produced by Addison’s disease, the adrenal cortex is destroyed, leading to impaired hormonal secretion and dysfunction.

2. Is adrenal insufficiency potentially fatal?
   Ans. With the right care and safety measures, someone with adrenal insufficiency can lead a normal life. Untreated conditions including high potassium, low sodium, and low sugar levels in the body linked to low blood pressure can have fatal consequences.

3. What do you mean by steroid hormones?
   Ans. Steroid hormones are all hormones that are biochemically steroid-like. Since lipids constitute the foundation of these macromolecules, they are called fat-soluble hormones and naturally come from cholesterol. The two groups of steroid hormones are corticosteroids and sex steroids, which are both secreted by the adrenal cortex and the gonads, respectively.

4. Write a note on catecholamines?
   Ans. Catecholamines are natural amines with neurotransmitter properties. Chemically, they are benzene rings with hydroxyl amine groups. Stress manifestation functions are carried out by the catecholamines the adrenal medulla secretes.

5. What is the function of hypothalamus?
   Ans. The brain region with endocrine functions is called the hypothalamus. It secretes hormones that regulate the pituitary’s release of a variety of hormones that regulate a range of bodily functions.