Explanation

The heart consists of four chambers in which blood flows.

Blood enters the right atrium and passes through the right ventricle.

The right ventricle pumps the blood to the lungs where it becomes oxygenated.

Explanation

The Midbrain is the auditory relay centre and the centre that controls the reflex movements of the eyes. 

Explanation

The correct pathway of a nerve impulse is Receptors → CNS → Effectors. 

Receptors:

• These are specialized cells that detect stimuli (changes in the environment) like light, temperature, or pressure.
• They convert these stimuli into electrical signals.

CNS (Central Nervous System):

• This includes the brain and spinal cord.
• The sensory neurons transmit the electrical signals from the receptors to the CNS.
• In the CNS, the information is processed and a decision is made about how to respond.

Effectors:

• These are the organs or muscles that carry out the response.
• The CNS sends motor neurons to the effectors, which then trigger the muscle to contract or gland to secrete a substance. 

Explanation

A normal human has 23 linkage groups. 

A linkage group is defined as all the genes located on a single chromosome that tend to be inherited together.

The number of linkage groups in an organism is equal to its haploid number of chromosomes (n).

Humans have 46 total chromosomes, which are organized into 23 pairs (the diploid number, 2n).

The haploid number (n) in humans is 23, meaning there are 23 distinct types of chromosomes.

Therefore, there are 23 linkage groups in a normal human, corresponding to the 22 pairs of autosomes and one pair of sex chromosomes (XX in females or XY in males, considered as one linkage group in the general "normal human" context). 

Explanation

Central chemoreceptors that monitor the levels of CO₂ in the blood are primarily located in the medulla oblongata. 

Specifically, they are found on the ventrolateral surface of the medulla oblongata in areas such as the retrotrapezoid nucleus (RTN) and the medullary raphe.

These receptors are susceptible to changes in the hydrogen ion concentration (pH) of the cerebrospinal fluid (CSF), which is directly and rapidly influenced by arterial CO₂ levels, as CO₂ can easily cross the blood-brain barrier.

Explanation

The pons and the medulla oblongata, along with the midbrain (which together form the brainstem), control the transitions between wake and sleep.

The hypothalamus also plays a critical, overarching role as the primary control center for the sleep-wake cycle. 

Explanation

Receptor: Detects the stimulus (e.g., in the skin).

The component of a reflex arc that connects the sensory neuron to the motor neuron within the spinal cord is the association neuron, also known as an interneuron. 

Sensory neuron:

Transmits the nerve impulse from the receptor to the central nervous system (spinal cord).

Association neuron (Interneuron):

Located within the central nervous system, this neuron processes the information and relays the signal from the sensory neuron to the motor neuron.

Motor neuron:

Transmits the nerve impulse from the central nervous system to the effector.

Effector:

The muscle or gland that produces the response (e.g., a muscle fiber that contracts). 

Explanation

When the kidneys perform their osmoregulatory role under the influence of Antidiuretic Hormone (ADH), they produce hypertonic urine with a decreased volume. 

ADH promotes water reabsorption in the collecting ducts of the kidney, leading to more concentrated urine (hypertonic) and reduced urine output (decreased volume). 

Explanation

Involuntary muscles work without conscious control.

Muscle Types:

- Skeletal muscle → voluntary 

- Cardiac muscle (heart) → involuntary   

- Smooth muscle (walls of internal organs) → involuntary

Explanation

The main role of mRNA during protein synthesis is to carry genetic information for protein synthesis. 

mRNA functions as a messenger molecule, carrying the genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm, where the instructions are used to build proteins.