Biology 1 Marks Question

The cerebrum is the most developed.

The hypothalamus of the central neural system acts as a master clock.

The cochlea determines the pitch of a sound.

The Inner ear has three semi-circular canals forming cochlea. Cochlea is responsible for maintaining the body balance.

Aqueous humor and vitreous humor:

Aqueous humor	Vitreous humor
It is a thin, watery fluid present between the cornea and the lens.	It is a transparent gel present between the lens and the retina.

3. Blind spot

Solution:
Blind spot is the part where the optic nerve passes out of the retina. Photoreceptors are absent from this region.

Cerebral aqueduct.

Brain.

Right and left hemispheres of the cerebrum are connected by corpus callosum. Each hemisphere is divided into frontal lobe, temporal lobe, parietal lobe and occipital lobe.

Vestibular apparatus.

Impulse conduction depends upon:

1. permeability of axolemma (axon membrane).
2. Osmotic equilibrium between the axoplasm and extracellular fluid present outside the axon.

1. Hypothalamus.
2. Medulla.

1. Synaptic knobs.
2. Schwann cell.

Choroid layer.

Pinna collects the vibrations in the air and directs them to the ear.

1. Cerebral aqueduct.
2. Corpora quadrigemina.

It is to provide accommodation for a large number of neurons.

Eustachian tube helps in equalizing pressure on both sides of the eardrum.

Scala media.

Ciliary muscles.

Sympathetic nervous system and parasympathetic nervous system.

1. Sensory.
2. Neurons.

The cerebrum is the most developed.

A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, with or without a gap between them.

The hypothalamus of the central neural system acts as a master clock.

Nervous system and endocrine system.

1. In the sockets, called orbits.
2. Inside the spinal cord.

They are present in the taste buds located in the tongue.

They communicate through oval window and round window respectively.

Transmission of neural impulses.

The cochlea determines the pitch of a sound.

External auditory canal, → Ear drum, → Stapes, → Incus, → Malleus, → Cochlea.

Non-myelinated nerve fibre.

The efferent nerve fibres transmit motor impulses from CNS to the concerned tissues/ organs and form the motor or efferent pathway.

Cone cells.

Forebrain, which mainly includes cerebrum.

Sclera (outermost layer).

1. Synaptic vesicles are present in the synaptic knob, the bulb-like structures at the ends of the branches of axon.
2. They contain neurotransmitters.

Grey matter and white matter.

Eustachian tube.

Myelinated and non-myelinated.

1. The projecting ridge having hair cells, found in the base of the semicircular canals (called ampulla), is called crista ampullaris.
2.  

1. The projecting ridge found in the utricle and saccule of the vestibular apparatus, is called macula.
2. Both are receptors to maintain the balance of the body.

Threshold stimulus: It fires the signals in the neuron.

Synapse acts as a one-way valve because neurotransmitter is secreted at the terminal knobs of axon only. The dendrite membrane (postsynaptic membrane) has the specific protein receptor molecules to break this neurotransmitter.

The nose contains mucus-coated receptors which are specialised for receiving the sense of smell and are called olfactory receptors. These are made up of olfactory epithelium which consists of three kinds of cells. The neurons of the olfactory epithelium extend from theoutside environment directly into a pair of broad bean-sized organs called olfactory bulb. Olfactory bulbs are extensions of the brains limbic system.

Because there is no photoreceptor cell.

The Inner ear has three semi-circular canals forming cochlea. Cochlea is responsible for maintaining the body balance.

Forebrain.

Central neural (nervous) system, lies along the main central axis of the body.

Action potential.

The path followed by the stimulus upto eliciting a response in a reflex action is called reflex arc. The components and functions of a reflex are in a reflex action are as follows:

• Specific receptor receive a stimulus and set up a sensory impulse.
• Afferent neuron brings sensory impulse from receptor to central nervous system.
• Intermediate neuron transfers impulse from afferent neuron to efferent neuron.
• Efferent neuron carries motor impulse from central nervous system to specific effector.
• Effector is the organ/ gland, which functions according to the impulse received.

Internal ear.

The human brain is present in the cavity of skull called cranium but the brain is not in directly in contact with skull, it is protected by layers of connective tissue called meninges. There are three meaninges viz.

1. Dura mater (Hard mother).
2. Arachnoid mater.
3. Pia mater (Soft mother).

Neurons are excitable because their membranes are in a polarised state.

The ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump.

The crista and macula are the specific receptors of the vestibular apparatus of the internal ear responsible for maintenance of balance of the body and posture.

The main function of cochlea is to convert sound waves into neural impulses to be sent to the brain.

Intersensory association, memory, communication.

1. Perilymph.
2. Organ of Corti.

Gustatory and olfactory senses are interrelated. Sense of smell helps in enhancing the sense of taste. This is the reason we don't get proper taste of food when we suffer from common cold.

Synaptic cleft refers to the gap between the membranes of a pre-synaptic and post-synaptic neurons at the synapse.

Sensory organs detect all types of changes in the environment and send appropriate signals to CNS.

Aqueous humor and vitreous humor:

Aqueous humor	Vitreous humor
It is a thin, watery fluid present between the cornea and the lens.	It is a transparent gel present between the lens and the retina.

Inner parts of cerebral hemispheres and group of associated deep structures like amygdala, hippocampus and hypothalamus.

These are proferin protein present in the cytoplasm of the neurons.

Dendrites conduct nerve impulses towards the cell body and are called afferent processes (receiving processes).

Cranium.

Eustachian tube connects the middle ear cavity with the pharynx. It helps in equalizing the pressures on either sides of the ear drum.

Central nervous (neural) system and peripheral nervous (neural) system.

Hypo thalamus.

Neurons are specialised cells, which can detect, receive and transmit different kinds of stimuli.

In the forebrain, smell.

It contains the cell bodies of the neurons, which give a greyish appearance; hence, it is called grey matter too.

Crista ampullaris and macula.

Midbrain and hind brain.

Scotopic is low light vision and photopic is daylight vision.

The somatic nervous system controls the movements of the body by acting on the skeletal muscles (i.e., relays voluntary impulses from the CNS to skeletal muscles).

This process accounts for the greater speed of an impulse travelling along a myelinated neuron than along a non-myelinated one. It is upto 50 times faster than the non-myelinated nerve fibre.

Along with the hypothalamus, it is involved in the regulation of sexual behaviour, expression of emotional reactions, e.g., pleasure, excitement, rage and fear and motivation.

Fovea.

It transmits impulse (sensory) from tissues/ organs to the CNS and forms the sensory or afferent pathway.

The functional junction between two neurons, through which a nerve impulse is transmitted from one neuron to another.

Stapes.

They hold the lens in position attached to the ciliary body.

This system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body. So, it is also called involuntary nervous system.

1. Corpus callosum.
2. Thalamus.

Bioelectric/ electrochemical disturbance (change).

Rhodopsin and iodopsin.

Ears are involved in sense of vertigo. The semi-circular canals in the internal ear are responsible for this.

Hind brain.

1. Hearing
2. Body balance.

Fovea.

When the body is in circular motion on a merry-go-round the circular canals of the internal ear are also on circular motion. Once the merry-go-round stops, it takes time for fine silica particles in circular canal to come in rest. As they are responsible for maintaining the balance of the body so a sense of giddiness prevails till the time silica particles come into proper position.

Neurotransmitters are the chemicals involved in the transmission of nerve impulses across the synapse. e.g., acetylcholine, nor-adrenaline.

Visual cortex.

Gap junctions.